Media Release

Illegal immigration set to rise after Brexit, study shows

Illegal immigration is set to rise when EU freedom of movement is brought an end in Britain, a think-tank has predicted.

The Social Market Foundation said that ending free movement will lead more people to enter and remain in the UK illegally, ultimately increasing public concern about immigration issues.

Politicians promoting Brexit as a way to answer public anxieties over migration should be honest with voters about the likely consequences of ending free movement, to avoid a future political backlash over immigration, the SMF said. 

In a new paper called Back to the Future, the SMF assessed the history of other experiences in restricting immigration after scrapping liberal entry policies for workers and also countries attempting to enforce temporary labour programs of the type now proposed by the UK.

Historic examples include Britain’s decision to end the unrestricted entry of Commonwealth subjects in the 1960s, Germany’s experience with admitting temporary “guest workers” from the 1960s, and the US ending its labour program for Mexican workers in 1965.

Drawing lessons from those experiences, the SMF predicted that ending EU freedom of movement and restricting EU nationals’ right to enter and stay in Britain for work will have precisely the opposite effect on immigration patterns to the one many Brexit supporters say they want.

Without more political honesty about the likely impact of Brexit on immigration patterns, Britain risks repeating the recent US experience, where unaddressed concerns over immigration over the Mexican border were ultimately leveraged by Donald Trump to help him win the presidency.

History offers four key lessons about attempting to end freedom of movement policies for workers, the SMF paper concludes:

1.      Greater immigration restrictions on well-established existing immigration flows can lead to an increased permanent lawful immigrant population – “circular” migrants who previously moved back and forth between countries chose to settle in their new country, and new migrants enter through more permanent routes.

2.     Greater immigration restrictions applied to well-established existing immigration flows can lead to increased irregular migrant entry – some people who would have entered under free movement rules will instead arrive through new temporary work and study schemes, then overstay.   

3.     Greater immigration restrictions applied to well-established existing immigration flows can lead to increased irregular immigrant stay, and therefore an increased irregular immigrant population – the UK’s strong border controls but weaker in-country controls encourage overstaying and added to this will be those EU nationals who do not successfully apply under the EU Settlement Scheme to remain in the UK following Brexit, but remain in the UK without permission.

4.   An increasingly visible irregular immigrant population accompanied by increased immigration enforcement can give rise to greater public concern over immigration even if overall immigrant flows are reducing –the measures needed to deliver new immigration restrictions are likely to draw public attention to illegal immigration and lead to a heightened debate about ID cards and other approaches that would help better identify, track and address overstayers.

The paper highlights the contradictory political results of restrictive immigration policies.  US political anxieties over the Mexican border have risen in recent years – and contributed to the election of Donald Trump – even as the number of Mexicans crossing the border have fallen significantly.

Jonathan Thomas, SMF migration researcher and author of the report said:

“History suggests that people who expect ending free movement to take away their worries about immigration are going to be disappointed. Illegal immigration has not been a big part of British debate in recent years but the precedents suggest it could soon be high on the political agenda.”

“People who want to end free movement should be honest with the electorate about the possibility that it will create significant new challenges relating to illegal immigration. And people who support a liberal approach to immigration should engage constructively with the perfectly legitimate view that illegal immigration is a problem that policymakers should address.”

James Kirkup, SMF Director, said:

“If our leaders fail to have that honest conversation about the future of immigration after free movement ends, they risk creating the sort of conditions in Britain that helped Donald Trump become US president.

“There are too many people in British politics, in all parties, who believe an open approach to immigration is beneficial but fail to talk honestly to voters about the pros and cons of immigration. They should ask themselves what Nigel Farage and the Brexit Party could become in future if misplaced expectations trigger another political backlash over immigration.


The main historic case-studies highlighted in the paper are:

  • Commonwealth: Commonwealth subjects had freedom of movement until 1962 when the Commonwealth Immigrants Act was passed
  • Germany: from 1961 Germany operated a “guestworker” scheme allowing free movement from Turkey.  Restrictions were put in place from 1973
  • US/Mexico:  In 1942, the US began the “Bracero” temporary labour programme, allowing Mexican workers to enter the US without significant restrictions. The programme ended in 1965


For a full copy of the report or to arrange an interview, contact the SMF on 0207 222 7060  

Barbara Lambert, SMF media officer –

James Kirkup, SMF director –

The SMF declares all sources of funding and retains complete editorial independence of its publications. This report’s full title is “Back to the future: What history tells us about the challenges of post-Brexit UK immigration policy”. It was supported by Unbound Philanthropy, a grant-making foundation.

About the SMF:

The Social Market Foundation (SMF) is a non-partisan think tank. We believe that fair markets, complemented by open public services, increase prosperity and help people to live well. We conduct research and run events looking at a wide range of economic and social policy areas, focusing on economic prosperity, public services and consumer markets.  The SMF is resolutely independent, and the range of backgrounds and opinions among our staff, trustees and advisory board reflects this.

 The SMF retains complete editorial independence of its publications.


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