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Undocumented Migrants

Asked by Mr Andrew SnowdenConservativeHome OfficeTabled Answered 14 July 2026UIN 14511

The question

To ask the Secretary of State for the Home Department, what methodology was used to estimate the figure of 412,000 illegal migrants in the United Kingdom.

Answered by Alex Norris

The figure was derived from a review of Home Office case working systems and includes individuals who are believed to be in the UK and do not have valid leave recorded. The figure also includes foreign nationals who hold valid leave but are being considered for deportation following a criminal conviction, and reflects individuals known to the Home Office.

To be clear, this figure is not a definitive list of every illegal migrant in the UK. Rather, it is the number of cases contained within an internal Home Office workflow database, which the Department uses to support the prioritisation of case management and enforcement activity.

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