A group of influential MPs has said that the UK Border Agency faces a backlog of more than 275,000 failed migrants who need to be removed from the country.
Committee chairman, Labour MP Keith Vaz, said the agency appeared to have "acquired its own Bermuda Triangle".
The Home Office said the report raised "legitimate concerns" about issues it was aware of and was already tackling.
For the first time in their tri-annual report on the agency, MPs collated all categories of cases not yet resolved.
The committee said it would take the UKBA "years" to clear the backlog and it was concerned the agency might not have enough resources to do so.
The committee said the backlog included at least 150,000 migrants who had been refused permission to stay in the UK, 21,000 asylum cases and 3,900 foreign offenders living in the community.