Illegal Immigration - Key Topic

Updated 11 July, 2019

  • Ministers say they do not know the scale of illegal immigration.
  • No official estimate has been published since 2005.
  • Former senior Home Office personnel suggest that there are at least a million illegal immigrants here already.
  • An ex-head of border enforcement claims 150,000 people enter without permission or fail to depart each year (2,885 a week)
  • Our research finds a net increase in illegal immigration of at least 70,000 per year (see report).
  • 77% of the public see illegal immigration as a ‘serious problem’
  • 70-80% of the public support measures aimed at deterring illegal migrants from remaining in the UK (i.e. a compliant environment).
  • There has been a sharp decline in removals of those here illegally
  • Since 2012, grants of permission to stay for illegal migrants via routes that allow the regularisation of status appear to have increased significantly. We recommend that such routes be permanently closed as they only encourage more illegal immigration.
  • Each additional person staying on ‘costs the taxpayer between £4,255 and £7,820 per year through the use of public services such as health, education and welfare benefits’ (Government statistics).
  • There are serious enforcement failures. An ex-Home Office head of enforcement says the system looks to be in a state of ‘paralysis’.
  • Enforcement funding is entirely inadequate. The head of the immigration staff union notes that illegal immigrants 'have very little chance of being caught' due to the dearth of investment..
  • Border staff describe security at ports as ‘resourced to fail’.
  • Calls for an amnesty for illegals are absurd and must be rejected.

The Definition of an Illegal Immigrant

1. Illegal immigrants do not have the right to remain in the UK. They may have entered legally but failed to leave when they were required to do so. Alternatively, they may have entered the UK illegally.

Cost of illegal immigration for the UK

2. The substantial illegal population in the UK adds to the pressures on housing and public services while paying little, if any, tax. The government has estimated (see p.8) that each additional person staying on ‘costs the taxpayer between £4,255 and £7,820 per year through the use of public services such as health, education and welfare benefits’. These figures were calculated by apportioning public spending to the resident population in the UK.

3. In 2013, the government estimated that illegal immigration cost the NHS £330 million per year. The London School of Economics has estimated that the long term costs of benefits for illegal migrants could be £1.6 billion a year.

4. Illegal migrants can be exploited by employers who ignore safety and minimum wage legislation. In addition, illegal immigration displaces the UK-born from jobs and places negative pressure on the wages of the lowest paid. Illegal immigration has been linked to organised crime. In the government’s words, stronger efforts to tackle immigration abuse would ‘reduce the operation and profitability of organised crime’ (see 2013 Home Office document, p.7).

Entry to the UK

5.There are four main ways in which a person can become an illegal immigrant:

  1. By entering the country undetected in a clandestine way, such as being smuggled in on a lorry from Calais.
  2. By entering the country legally, either for a short visit or for work, study or family reasons, and then subsequently remaining after permission to remain here has expired.
  3. By failing to leave the country after a claim, and often also an appeal, for asylum has been rejected.
  4. Technically, a child has no right to remain in the UK if both parents are illegal immigrants.

6. The EU migrant crisis has had a significant impact on the UK in recent years although its effects have declined from the peak in 2015/16. Until the closure of the ‘Jungle’ camp in 2016 there were as many as 10,000 illegal immigrants camped out in the Calais region with the intention of making it to the UK, despite being in France, which is obviously a safe country.

7. Despite this, clandestine trips to the UK across the Channel remain a major problem. One source (Policy Exchange’s Border Audit, 2018) suggests that the average number of detected illegal lorry drops in recent years has been around 15,000 per year. In 2017 there were 30,000 recorded attempts to enter the UK illegally from northern France (Parliamentary Answer, 2018). Official statistics also revealed that only a third of 439 illegal migrants who were intercepted while crossing Channel to the UK in 2018 and early 2019 were returned to the safe country of France (also see article by Migration Watch UK).

The scale of the problem

8. By its nature, illegal immigration is very difficult to measure, although it was announced in June 2019 that the ONS and Home Office statisticians have been ‘working with departments across the Government Statistical Service and academics to explore possible approaches to measuring illegal immigration’ and have speculated on various possible methodologies. The Census does not record the immigration status of respondents and, in any case, most illegal immigrants would be very unlikely to respond.

9. In 2005 the Home Office estimated that in 2001 the population of illegal immigrants was approximately 430,000, excluding the UK born children of illegal immigrants.

10. In 2009, the London School of Economics produced an estimate of the illegal immigrant population in 2007; they suggested a central figure of 670,000 using a similar methodology to the 2005 estimate.

11. In 2010 Migration Watch UK estimated the illegal immigrant population to be 1.1 million (a figure later echoed by former top officials). In 2017 a former Head of Immigration Enforcement, David Wood, and previous Home Office (HO) speechwriter Alisdair Palmer claimed that the HO estimated that each year as many as 150,000-250,000 foreign nationals failed to return home when they should or entered illegally. Some will eventually go home. To read Wood and Palmer's full report click here.

12. Our research, based upon available data, estimates a net rise in illegal immigration of just under 70,000 per year (see report) – nearly equivalent to the size of the full-time British Army.

13. In April 2015 the government reintroduced exit checks allowing the authorities to know who had departed the country. While they appear to have been useful in providing clarity on the scale of compliance by those on study visas in particular, the Exit Checks have been criticised for failing to use information regarding nationals from more than 50 countries whose citizens are not required to obtain a visa to visit for up to six months (these account for the majority of visitors to the UK).

14. Indeed, the Independent Chief Inspector of Borders and Immigration (ICIBI) found in late 2017 that the Exit Checks did not contain evidence of departure for more than 600,000 people who were required to depart the UK between 2015 and 2017 (85% of these, or more than 510,000 people, were non-visa nationals – see p.20 of report). It remains unclear whether the Home Office has addressed this by including a routine operational assessment of non-visa nationals. If this has not been done yet it should clearly be expedited.

Assessment of enforcement efforts

15. The number of illegal immigrants removed from the UK is very low in comparison to the size of the illegal population. In 2018, there were just 9,400 enforced returns (a drop of a third in five years) and 15,000 voluntary returns - a fall of more than 10,000 since 2014.

Figure 1: Returns of those with no right to be here, 2014-18, HO.

16. There are an average of 25,400 asylum applications every year. Yet fewer than half of these applications for asylum have ultimately been granted, even taking into account those successful on appeal. Those whose asylum claim has been rejected do not have permission to remain in the UK and are required to depart.

17. However, on average, over 60% of those who were refused asylum or some other form of international protection after having applied for it during the period 2004-2017 did not leave the country. This amounts to nearly 120,000 failed asylum seekers remaining here over the entire period, or 8,500 people per year (a number have been granted amnesty by stealth – in 2011 it was revealed that the government had given settlement to over 160,000 people as part of what was called a ‘backlog clearance’ exercise, including failed asylum seekers).

18. Despite a larger number of overall applications, removals of failed asylum seekers have dropped by nearly two-thirds over the past decade, from 11,600 per year to just over 4,000 in 2018.

Figure 2: Removals of failed asylum claimants, 2009-18. HO.

19. In 2017, the ICIBI reported that there was ‘little evidence that effective action was being taken to locate the vast bulk’ of 55,000 illegal immigrants - including failed asylum seekers, immigration offenders and foreign national offenders - of whom the Home Office (HO) had lost track. The HO should urgently report to the public on its progress.

Obstacles to Enforcement

20. The Chief Inspector of Borders has said that the Windrush affair has made officials less willing to remove illegal immigrants from the UK. However, there is no reason why a bureaucratic failure primarily affecting people with a right to be here should lead to a condoning of illegal immigration, in clear contravention of the public’s wishes. Doing so can only be manna for traffickers who profit by encouraging people to break the law and put their lives at risk needlessly in perilous cross-Channel journeys.

21. Meanwhile, the view of a former chief of immigration enforcement is that ‘there is a whole system breakdown… The message to people here illegally is that there is no serious response by the authorities. From what I hear there is paralysis.’

22. An effective system to remove those who have no right to remain in the country is essential to the credibility of border control. That credibility is at risk. The declining effectiveness of removals can only further encourage people to put their lives at risk and depress public confidence in immigration control.

23. There is a great deal of public support for tackling illegal immigration. 77% of the public said it was a serious concern (Project28 poll, 2018). Meanwhile, between 70% and 80% of the public support ‘compliant environment’ measures aimed at making it difficult for illegal migrants to remain in the UK (YouGov, April 2018).

24. It is deeply concerning that, as was reported in July 2019, more than £10 million of taxpayers’ money has been spent by the government in five years on ‘phantom’ flights to deport failed asylum seekers that were then abandoned before take off. According to the latest Home Office accounts, the bill for cancelled repatriation flights was just over £2 million in 2018.

25. Insufficient resources are being allocated to enforcement. In 2018/19, gross expenditure was just under £462 million – about a twentieth of one percent of total government spending in that year.

26. The head of the Immigration Services Union has said that illegal immigrants ‘have very little chance of being caught’ due to the dearth of investment in enforcement. Meanwhile, a former chief executive of the Border Agency warned that the government ‘does not have the resources or political levers’ to deal with this issue and noted that insufficient attention was being paid to the number of non-EU migrants working here illegally (The Times).

27. An additional impediment is the size of the detention estate. At present only around 3,500 can be held in detention at any one time. This is clearly inadequate compared to the size of the task.

28. The lack of return agreements between the UK and source countries is a further problem (a returns agreement is one whereby two countries agree to return their nationals to each other when they are found illegally in each other’s territory).

29. The UK does not have such agreements with countries (e.g. Brazil / Bangladesh) thought to be significant sources of illegal immigration.

30. Another material factor is a lack of documentation. Some illegal immigrants will not have had documents i.e. a passport, when they arrived. Others will have purposely destroyed documents to frustrate the returns process. Some countries refuse to re-document their own citizens. Others, such as India, make it as difficult as possible.

31. The government should encourage source countries to re-document their citizens who are illegally present in the UK. It should also encourage cooperation by linking it to the possible removal of visa-free access (e.g. for Brazil) - or where applicable, to aid provision.


32. Although there is a lack of clarity in the official statistics on this topic, the number of grants of leave to those with no right to be in the UK appears to have increased significantly in recent years. Regularisation  means that the person goes from being someone with no right to remain to being a legal migrant with either temporary or indefinite leave to remain.

33. There were 41,300 extensions of stay under the ‘Family life’ (ten year route) in 2018 (a 45% increase on the previous year). The increase may have been linked to an August 2017 Supreme Court ruling (see summary) that expanded use of the Family Life (ten-year route). Typically those making an attempt to stay under this route are overstayers at the time of application.

34. There were also 6,200 extensions of leave to remain under the ‘Private life’ route (a 56% increase on the previous year). This latter route includes the rule covering those with periods of overstay who have 20 years of continuous residence (see more here), the ‘seven-year residence rule for children and families’ (introduced in 2012), the ‘half of life’ rule for under 25s and the ‘very significant obstacles to integration’ rule.

35. The Home Office also issued around 2,200 grants of leave to remain on a discretionary basis as well as 3,400 labelled as ‘Other’, some of whom may have been illegal migrants being granted leave to remain.

36. The number of people regularising status via such routes has risen in recent years – amounting to a significant addition to the UK population via the back door. We recommend that all such routes be urgently closed as they are entirely unfair to migrants who go through the proper channels, undermine the rule of law and potentially risk lives by further encouraging illegal immigration.

What else should be done?

37. We have also suggested the following:

  1. Compliant environment legislation should be urgently reinstated and strengthened (with additional oversights based upon lessons learned from Windrush in order to ensure fair implementation)
  2. There should be more widespread use of Assisted Returns.
  3. To address the ‘paralysis’ in immigration enforcement, funding (currently £461m) should be doubled to £1 billion, with a view to further increases in future.
  4. Funding for the Border Force (currently £560m) should be increased by 50% in order to ensure adequate security at UK ports.
  5. A much larger share of immigration offenders and failed asylum seekers in the 80,000 reporting population should be detained until being removed.
  6. To assist in the process there needs to be a major increase in the size of the detention estate.
  7. The government should establish one-stop shops at detention centres for the speedy processing of the backlog of asylum claims. An important component of this is the re-introduction of the Detained Fast-Track policy (which appears to have been delayed, despite being announced in 2017).
  8. If the Home Office cannot effectively deal with the backlog of removals, or with some future major inflow, the government should not rule out the use of the armed forces in aid of the civil administration (for more, see our paper: ‘MW368 - Lessons from Calais’).

Irresponsible calls to turn a blind eye to illegal immigration

38. Those who knowingly enter the UK without permission or overstay are guilty of a criminal offence (see Section 24 the Immigration Act 1971). Yet 129 MPs recently signed a pledge to not report suspected illegal migrants to authorities. Such a move amounts to deliberately ignoring illegal behaviour and is grossly irresponsible.

39. Meanwhile, calls for an amnesty are absurd. In countries where they have been tried they have simply added to the number of illegals (see our paper). Furthermore, an amnesty would of course reward illegal behaviour while being grossly unfair to migrants who go through the correct channels. It would also extremely expensive for the taxpayer (see our paper – ‘The financial case against an amnesty for illegal immigrants’).


40. The government has a duty of care to protect and enforce the UK’s borders. Illegal immigration is a serious failure of governance. There appears to be ‘paralysis’ in enforcement while the number of people whose presence has been legalised as a result of ‘amnesty-by-stealth’ has massively increased since 2012. This only serves to encourage the UK to be seen increasingly as a soft touch while the problem and backlogs become more intractable. The new Prime Minister should set an entirely new course, reinstating the deterrent of enforcement and ruling out any kind of amnesty.