How Many Illegal Immigrants Are in the UK?
The exact number of people living in the UK without valid immigration permission is not known. The most recent widely cited national estimates relate to 2017, not 2025 or 2026.
A revised Pew Research estimate placed the UK’s unauthorised migrant population at approximately 700,000 to 900,000 in 2017. A separate Greater London Authority estimate produced a central figure of 674,000, rising to 809,000 when UK-born children of unauthorised migrants were included. These figures are estimates, not confirmed counts, and the real number may have changed significantly since 2017.
There is no official current count showing exactly how many illegal or unauthorised immigrants live in the UK.
The best-known recent national estimates are based on 2017 data:
- Revised Pew estimate: 700,000 to 900,000
- Greater London Authority central estimate: 674,000
- GLA estimate including UK-born children: 809,000
Because migration status changes over time and unauthorised residents are difficult to measure, these figures should not be presented as a confirmed total for 2025 or 2026.
Key UK Immigration Figures at a Glance
| Measure | Latest figure available | Reference period |
| Estimated unauthorised migrant population | 700,000–900,000 | 2017 estimate |
| GLA central unauthorised estimate | 674,000 | 2017 estimate |
| GLA estimate including UK-born children | 809,000 | 2017 estimate |
| Total non-UK-born population | 13.115 million | June 2024 |
| EU+ born population | 3.871 million | June 2024 |
| Long-term immigration | 813,000 | Year ending December 2025 |
| Net migration | 171,000 | Year ending December 2025 |
The ONS estimated that 13.115 million UK residents were born outside the UK in June 2024, including 3.871 million people born in EU+ countries. It separately estimated 813,000 long-term immigrants and 171,000 net migration in the year ending December 2025. These figures measure different things and should not be confused with the unauthorised migrant population.
How Many Illegal Immigrants Are in the UK?
The phrase “illegal immigrants” is widely searched, but there is no single live government database showing everyone living in the UK without valid residence permission.
Researchers instead estimate the population using indirect methods.
What Is the Latest Estimate of Illegal Immigrants in the UK?
The two most recent widely discussed national estimates relate to 2017.
The Greater London Authority estimated approximately 674,000 unauthorised migrants, increasing to 809,000 where UK-born children of unauthorised migrants were included.
Pew Research originally estimated between 800,000 and 1.2 million, but that estimate was retracted in March 2025 and revised down to approximately 700,000 to 900,000.
Why Is the Figure an Estimate Rather Than a Confirmed Count?
People without valid immigration permission may not appear fully in population surveys, administrative datasets or other official systems.
Some may also:
- Leave the UK
- Regularise their immigration status
- Receive a new visa or other permission
- Have an asylum claim decided
- Move between different immigration categories
- Die or otherwise leave the resident population
Because of these changes, any estimate becomes less reliable as time passes.
How Many Illegal Immigrants Were in the UK in 2025?
There is no authoritative national estimate showing the exact unauthorised migrant population in 2025.
Figures published or discussed in 2025 may still rely on older underlying data. For example, the revised Pew estimate publicised in 2025 still relates to the UK’s estimated unauthorised population in 2017.
This distinction is essential for accurate reporting.
Can Small-Boat Arrivals Be Used as the 2025 Total?
No.
Small-boat arrival statistics measure a specific form of entry during a particular period. They do not measure the number of unauthorised migrants currently living in the UK.
Some people arriving irregularly claim asylum and have a distinct legal position while their claim is considered. Others may later leave, receive permission or be removed.
Arrival data therefore cannot be used as a substitute for the total resident unauthorised population.
Why Is It Difficult to Count Illegal Immigration in the UK?
Estimating an unauthorised population is inherently difficult because it involves people who may not appear in standard immigration or household datasets.
Visa Overstayers Are Difficult to Measure
Some people enter the UK lawfully and later remain after their permission expires.
Their original arrival may be recorded, but determining whether they remain in the UK after expiry can be more difficult.
Some People Leave Without Being Reflected Immediately
A person who was previously unauthorised may later leave the UK.
Depending on the dataset and method, that departure may not immediately be reflected in an estimate.
Immigration Status Can Change
An unauthorised migrant may later receive permission to remain.
Similarly, someone who originally had valid permission may later become an overstayer.
The population is therefore constantly changing.
Surveys May Undercount Some Groups
People who are worried about their immigration status may be less likely to participate in household surveys or may live in circumstances that make them harder to reach.
Definitions Also Differ
Some estimates include groups that others exclude.
For example, one study may include UK-born children of unauthorised migrants while another may not. Some may treat asylum seekers differently depending on their legal status.
Small Heading: No Single Database Contains Every Unauthorised Migrant
This is why responsible reporting should use a range or estimate and state the reference year clearly.
How Are Estimates of Illegal Immigration Calculated?
A common approach is known as the residual method.
What Is the Residual Method?
In simplified terms, researchers:
- Estimate the total foreign-born or migrant population.
- Estimate how many people have lawful immigration status.
- Subtract the lawful-status estimate from the wider migrant population.
- Adjust for uncertainties and groups that may be missing from the data.
Both the GLA and Pew estimates referenced above used versions of this approach.
What Data Sources Can Be Used?
Researchers may draw on:
- Census information
- Population surveys
- Visa records
- Asylum data
- Immigration enforcement records
- Administrative data
- Estimates of departures
- Mortality and population-change data
Why Do Different Studies Produce Different Numbers?
Results can vary because researchers make different assumptions about:
- Which groups should be included
- How many overstayers remain in the country
- How many people have left
- Whether asylum seekers are included
- Whether UK-born children are counted
- Which reference year is used
This is why a single headline figure should never be presented without methodology and date.
What Is Immigration?
Immigration is the movement of people into a country to live there temporarily or permanently.
A person moving from another country to live in the UK is immigrating to the UK.
What Does “Immigrate” Mean?
To immigrate means to move into another country to live there.
For example, a person who moves from France to the UK is immigrating to the UK.
Immigration vs Emigration
Immigration refers to people moving into a country.
Emigration refers to people moving out of a country.
What Is an Immigrant?
An immigrant is generally a person who has moved from another country to live in the UK.
However, statistics can define this population in different ways.
Foreign-Born Resident
A foreign-born resident is someone living in the UK who was born outside the UK.
This includes people who may now be British citizens.
Foreign National
A foreign national is someone who does not hold British nationality.
A foreign-born person and a foreign national are not always the same thing.
A person born abroad may later become British, while someone born in the UK may hold another nationality.
What Is an Illegal or Unauthorised Immigrant?
The phrase “illegal immigrant” is commonly used in public debate and search queries, but it can oversimplify a person’s immigration position.
More precise terms include:
- Unauthorised migrant
- Irregular migrant
- Undocumented migrant
- Person without valid immigration permission
What Is an Unauthorised Migrant?
An unauthorised migrant is generally a person living in a country without valid legal permission to reside there.
The Migration Observatory notes that terminology varies and that different studies may use different definitions.
What Is an Irregular Migrant?
“Irregular migrant” is another term often used for someone whose immigration status does not comply with the legal requirements for residence.
What Is an Undocumented Migrant?
“Undocumented migrant” is often used to describe someone without valid residence documents, although a person may technically possess identity documents while still lacking lawful immigration permission.
Which Term Is Most Accurate?
For legal and statistical content, unauthorised migrant or person without valid immigration permission is often clearer than using “illegal immigrant” as a blanket label.
Who May Be Counted as an Unauthorised Migrant in the UK?
Different studies may include different groups.
Visa Overstayers
A person may enter the UK legally with a visa and remain after that permission expires.
This is one route into unauthorised residence.
People Who Enter Without Immigration Permission
Some people enter the UK without the required immigration permission or through an unauthorised route.
People Who Remain After an Asylum Claim Is Finally Refused
A person whose asylum claim and any available appeal rights have ended may become liable to leave the UK if they have no other permission to remain.
Children Born in the UK
Some population estimates include UK-born children of parents without lawful immigration status, while others do not.
This is one reason why published totals can differ substantially.
Who Should Not Automatically Be Called an Illegal Immigrant?
Several immigration categories should not be conflated.
People With Pending Asylum Claims
A person with a pending asylum claim has a particular legal position while the claim is being determined.
They should not automatically be described as an unauthorised resident.
Recognised Refugees
A recognised refugee has been granted protection and lawful immigration status.
People With Valid Visas
Someone with valid work, student, family or other immigration permission is lawfully present subject to the conditions of that permission.
People With Indefinite Leave to Remain
A person with indefinite leave to remain has settled immigration status.
British Citizens Born Abroad
A person may have immigrated to the UK and later become a British citizen.
They may still be foreign-born for statistical purposes but are no longer a foreign national.
How Many Immigrants Are in the UK?
The latest ONS rolled-forward estimate shows that approximately 13.115 million people living in the UK in June 2024 were born outside the UK.
This is the best current measure for the broad question “how many immigrants are in the UK?” when using country of birth as the definition.
How Many UK Immigrants Are There?
Using the ONS non-UK-born measure, approximately 13.1 million UK residents were born abroad in June 2024.
This does not mean that all 13.1 million are foreign nationals or recent arrivals.
Does This Include Legal and Illegal Immigration?
The non-UK-born population includes people with many different statuses, including:
- British citizens born abroad
- People with settled status
- People with indefinite leave to remain
- Work visa holders
- Student visa holders
- Family visa holders
- Refugees
- Other migrants with lawful status
- An estimated unauthorised population
The overwhelming category “foreign-born” therefore does not mean “illegal immigrant”.
Immigrant Population vs Immigration vs Net Migration
These figures answer different questions.
Immigrant Population
This means the number of migrants already living in the UK.
The ONS estimated the non-UK-born population at 13.115 million in June 2024.
Annual Immigration
Annual immigration measures people moving to the UK for the long term during a specified period.
The ONS provisionally estimated 813,000 long-term immigrants in the year ending December 2025.
Emigration
Emigration measures people leaving the UK to live abroad for the long term.
Net Migration
Net migration is immigration minus emigration.
The provisional UK net migration figure for the year ending December 2025 was 171,000.
Small Heading: Different Immigration Statistics Answer Different Questions
A resident population figure should not be compared directly with annual immigration or net migration without explaining the difference.
How Many European Immigrants Are in the UK?
The ONS estimated that approximately 3.871 million UK residents were born in EU+ countries in June 2024.
What Does EU+ Mean?
The ONS EU+ grouping includes EU countries plus certain associated European countries under its statistical classification.
European-Born Residents vs European Nationals
A European-born resident may now hold British citizenship.
Similarly, someone may hold an EU nationality but have been born elsewhere.
Country of birth and nationality therefore produce different totals.
Has European Migration Changed?
The ONS estimated that the EU+ born population declined slightly between June 2022 and June 2024, while the non-EU+ born population increased.
Can Immigrants Vote in the UK?
Some immigrants can vote in UK elections.
Eligibility depends on:
- Nationality
- Immigration status
- Residence
- Age
- The type of election
- Whether the person lives in England, Scotland, Wales or Northern Ireland
The Electoral Commission confirms that British, Irish and qualifying Commonwealth citizens can meet the nationality requirement for UK Parliamentary elections.
Can Immigrants Vote in a UK General Election?
British citizens, Irish citizens and qualifying Commonwealth citizens may be eligible to vote in UK Parliamentary elections, provided they satisfy the other registration requirements.
Can EU Citizens Vote in the UK?
EU citizens do not generally gain the right to vote in UK Parliamentary elections solely because they are EU citizens.
However, eligibility for local and devolved elections varies according to nationality, residence and the part of the UK involved.
Voting Rules in Scotland
The Electoral Commission states that qualifying foreign nationals living in Scotland may register where they have permission to enter or stay in the UK, or do not require such permission.
Voting Rules in Wales
Wales also has broader registration rules for some qualifying foreign citizens in devolved and local elections.
Can Illegal Immigrants Vote in UK Elections?
A person living in the UK without valid immigration permission will generally not satisfy immigration-status conditions that apply to certain qualifying foreign or Commonwealth voter categories.
However, the legal test is based on nationality, residence, immigration permission and election type rather than the broad label “immigrant”.
Does Having a Visa Give You the Right to Vote?
Not automatically.
A work, student or family visa does not by itself grant voting rights.
Nationality and the type of election remain central.
Can Someone Be an Immigrant and Still Have Full Voting Rights?
Yes.
A person can be an immigrant and also be:
- A British citizen
- An Irish citizen
- A qualifying Commonwealth citizen
Immigrant status and voter eligibility are not opposites.
Do Illegal Immigrants Get Free Healthcare in the UK?
Some NHS services are available without charge regardless of immigration status, but this does not mean that all NHS treatment is free for everyone.
The detailed charging guidance cited here relates primarily to England. Scotland, Wales and Northern Ireland operate under their own healthcare rules and regulations.
Can Undocumented Migrants Register With a GP?
Yes.
In England, GP and nurse consultations in primary care are free to everyone, and GP practices are not required to demand proof of address or immigration status as a condition of registration.
Is A&E Free?
Accident and emergency services are generally among the NHS services that can be provided without charge under the overseas visitor charging framework.
However, treatment following admission to hospital may be subject to different charging rules.
Which NHS Services Are Free?
In England, free services can include:
- GP and nurse consultations in primary care
- Certain emergency services
- Diagnosis and treatment of specified infectious diseases
- Certain sexual-health services
- Certain family-planning services
- Treatment connected with specified forms of violence
The exact rules depend on the service and circumstances.
Can Illegal Immigrants Be Charged for Hospital Treatment?
Yes.
NHS hospital treatment in England is generally residence-based. Someone who is not ordinarily resident and does not qualify for an exemption may be charged for secondary care.
Do Asylum Seekers Get Free NHS Healthcare?
Asylum seekers and some other protected or exempt groups can qualify for exemptions from NHS hospital charges.
Refused asylum seekers may also receive certain NHS services free of charge, including A&E and specified infectious-disease treatment.
Does GP Registration Make Hospital Treatment Free?
No.
Being registered with a GP does not automatically establish entitlement to free secondary-care treatment.
Small Heading: Free NHS Access Does Not Mean Every Treatment Is Free
Healthcare entitlement depends on the service, the person’s status and the rules applying in the relevant UK nation.
Are Small-Boat Arrivals the Same as Illegal Immigration?
No.
Small-boat arrivals are a measure of people arriving through a particular route.
The unauthorised migrant population measures people living in the UK without valid residence permission.
These are different concepts.
Do People Arriving by Small Boat Claim Asylum?
Many people who arrive irregularly make asylum claims.
While a claim is pending, their legal position is different from that of someone simply remaining without any outstanding protection claim.
Why Small-Boat Arrivals Cannot Be Used as the Total
The total unauthorised population may include:
- Visa overstayers
- People who entered through other routes
- People whose permission expired
- People remaining after final immigration decisions
Equally, not every irregular arrival remains unauthorised indefinitely.
Illegal Immigration vs Asylum in the UK
Asylum and unauthorised immigration should not be treated as identical.
What Is an Asylum Seeker?
An asylum seeker is someone asking the UK for protection because they claim they would face persecution or serious harm if returned.
What Is a Refugee?
A refugee is someone whose protection claim has been recognised.
Is Seeking Asylum Illegal?
Making an asylum claim is a legal process.
A person’s route of arrival and their asylum claim are separate legal questions.
What Happens After a Claim Is Refused?
If a claim is finally refused and the person has no further appeal rights or other permission to remain, they may become liable to leave the UK.
Why UK Immigration Numbers Are Often Misunderstood
Immigration statistics are frequently compared even though they measure entirely different things.
Illegal Immigration vs Total Immigration
The estimated unauthorised population is only one part of the broader migrant population.
Immigrants vs Foreign Nationals
A foreign-born resident may be British.
Small-Boat Arrivals vs Resident Population
One is an arrival flow. The other is a resident stock.
Immigration vs Net Migration
Immigration counts arrivals. Net migration subtracts departures.
Estimates vs Administrative Records
Some figures are derived from statistical models rather than direct counting.
Small Heading: Always Check What a Number Measures Before Comparing It
The date, definition and methodology are just as important as the headline figure.
Key UK Immigration Figures Explained
| Question | Best figure to use | Important qualification |
| How many illegal immigrants are in the UK? | 700,000–900,000 | Estimate based on 2017 |
| How many immigrants are in the UK? | 13.115 million | Non-UK-born population, June 2024 |
| How many European immigrants are in the UK? | 3.871 million | EU+ born population, June 2024 |
| How many people immigrated to the UK in 2025? | 813,000 | Long-term arrivals, not resident population |
| What was UK net migration in 2025? | 171,000 | Immigration minus emigration |
What Should You Do If You Do Not Have Valid UK Immigration Status?
If you believe your visa has expired or you may not have valid permission to remain, your options depend on your individual immigration history.
Check Your Current Immigration Position
Review:
- Your visa or eVisa expiry date
- Previous Home Office decisions
- Any pending application
- Any appeal or administrative review
- Home Office correspondence
- Your travel history
Check Whether You Have a Possible Route to Remain
Depending on the circumstances, possible issues may include:
- Family life in the UK
- Private life
- Long residence
- Human rights
- Asylum or protection
- A route based on a partner, parent or child
- Another immigration category
A general article cannot determine whether a particular person qualifies.
Do Not Assume You Have No Options
Immigration status can be legally complex.
A previous refusal or period without valid permission does not necessarily answer every question about future eligibility.
Speak to a UK Immigration Solicitor About Your Status
If your immigration position is uncertain, obtaining advice before making another application or contacting the Home Office about a complex case can help you understand the available routes and risks.
Frequently Asked Questions About Immigration in the UK
How Many Illegal Immigrants Are in the UK?
There is no exact official current count. The most recent widely cited national estimates relate to 2017. A revised Pew estimate placed the figure at approximately 700,000 to 900,000, while the GLA produced a central estimate of 674,000.
How Many Illegal Immigrants Were in the UK in 2025?
There is no authoritative national estimate specifically measuring the unauthorised resident population in 2025. Estimates discussed in 2025 may rely on substantially older data.
How Many Immigrants Are in the UK?
The ONS estimated that 13.115 million UK residents were born outside the UK in June 2024.
How Many UK Immigrants Are There?
Using country of birth as the measure, approximately 13.1 million UK residents were non-UK-born in June 2024.
How Many European Immigrants Are in the UK?
Approximately 3.871 million UK residents were born in EU+ countries in June 2024, according to the ONS.
What Is Immigration?
Immigration is the movement of people into another country to live there temporarily or permanently.
What Is an Immigrant?
An immigrant is generally someone who has moved from another country to live in the UK.
What Does Immigrate Mean?
To immigrate means to move into another country to live there.
What Is an Illegal Immigrant?
The phrase is commonly used for someone living in a country without valid immigration permission. “Unauthorised migrant” or “person without valid immigration permission” is often more precise.
Is an Asylum Seeker an Illegal Immigrant?
Not automatically. Someone with a pending asylum claim has a distinct legal position while that claim is being considered.
Is a Refugee an Illegal Immigrant?
No. A recognised refugee has been granted lawful protection status.
Is a Visa Overstayer an Illegal Immigrant?
A person who remains after their immigration permission expires may become an overstayer and may no longer have lawful permission to remain, subject to the precise circumstances.
Are Small-Boat Arrivals Included in Illegal Immigration Estimates?
Not automatically. Arrival figures and unauthorised resident-population estimates measure different things.
Can Immigrants Vote in the UK?
Some can. British, Irish and qualifying Commonwealth citizens may be eligible in UK Parliamentary elections, while rules for EU and other foreign citizens vary for local and devolved elections.
Can Illegal Immigrants Vote in UK Elections?
A person without valid immigration permission will generally not satisfy immigration-status conditions applying to certain qualifying voter categories. Eligibility also depends on nationality and election type.
Can EU Citizens Vote in UK Elections?
Some EU citizens can vote in local or devolved elections depending on nationality, residence, status and the UK nation involved. EU citizenship alone does not generally give a right to vote in UK Parliamentary elections.
Do Illegal Immigrants Get Free Healthcare in the UK?
Some NHS services are free regardless of immigration status, including GP consultations in England. Hospital treatment may be chargeable unless an exemption or other entitlement applies.
Can an Undocumented Migrant Register With a GP?
Yes. In England, a GP practice should not require proof of immigration status or address as a condition of registration.
Is A&E Free for Undocumented Migrants?
A&E services can be provided without charge, but subsequent hospital treatment may be subject to charging rules.
Do Asylum Seekers Get Free NHS Healthcare?
Certain asylum seekers and protected groups may be exempt from NHS hospital charges. The exact position depends on status, service and the applicable UK healthcare system.
Understanding UK Immigration Statistics Correctly
The most important point is that there is no exact current count of unauthorised migrants living in the UK.
The best-known estimates are older and should be presented with their reference year and methodology.
At the same time, broader UK immigration numbers should not be confused:
- Around 13.115 million residents were non-UK-born in June 2024.
- Around 3.871 million were EU+ born.
- Long-term immigration was provisionally 813,000 in the year ending December 2025.
- Net migration was provisionally 171,000 over the same period.
- The unauthorised migrant population is a separate estimated category.
Need Advice About Your UK Immigration Status?
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