Mr Frank Field (Birkenhead, Labour): To ask the Secretary of State for the Home Department what recent estimate she has made of the number of illegal immigrants in the UK.
Mr Harper:The clandestine nature of irregular migration and the lack of a common definition mean that it is difficult to produce estimates of the illegal migrant population in the UK.
In the last decade there have been two estimates of the illegal migrant population in the UK, giving central estimates of 430,000 (range 310,000 to 570,000) in 2001 (Woodbridge, J. “Sizing the Unauthorised (Illegal) Migrant Population in the United Kingdom in 2001.” Online Report 29/05, Home Office, London, 2005) and 618,000 (range 417,000 to 863,000) in 2007 (Gordon I., K. Scanlon, T. Travers, and C. Whitehead. “Economic Impact on London and the UK of an Earned Regularisation of Irregular Migrants in the UK.” GLA Economics, Greater London Authority, London, 2009.).
The 2012 European Migration Network report ‘Practical Measures for Reducing Irregular Migration’ (Toms and Thorpe, 2012)
http://emn.intrasoft-intl.com/Downloads/download.do; jsessionid =BB91F016906F64A5AD8BD0C1D8BA1586?fileID=2909
sets out the current UK evidence on the illegal migrant population.