A parliamentary committee in Britain says more than 275,000 people are in the country illegally or without the knowledge of the UK Border Agency.
The committee said it would take years for the agency to clear the backlog of illegal immigrants and overstayers.
Committee chairman Labour MP Keith Vaz said the agency appeared to have ''acquired its own Bermuda Triangle'' and the backlog of cases awaiting resolution was ''now equivalent to the entire population of Newcastle upon Tyne''.
''It's easy to get in, but near impossible to keep track of anyone, let alone get them out,'' he said.
The BBC reports the committee said the backlog included:
At least 150,000 migrants who had been refused permission to stay in Britain, 21,000 asylum cases, 80,000 asylum applications and 21,500 immigration cases where the agency had lost track of the applicant.