The number of missing migrants in Britain is now equal to the population size of Sheffield, a group of MPs has said.
The Home Affairs Select Committee said the number of unresolved immigration cases has hit 564,222.
The committee reached the figure following the publication of chief inspector of borders and immigration John Vine’s latest report on overstayers in Britain.
MP Keith Vaz, chairman, said there was also a backlog of cases being dealt with at the Home Office.
He added: “In addition to this is the Government’s missed immigration target. “Our immigration system has left A&E and has entered intensive care.”
The Commons committee said a failure to introduce a system of “counting everyone in, and everyone out” of Britain before the next general election may increase security risks and illegal immigration.