The UK Border Agency is still failing in its "basic functions" in spite of efforts to overhaul it, MPs have said.
The home affairs committee said UKBA had provided "inconsistent" information about immigration and asylum cases dating back to 2006 and this backlog would take four more years to clear.
It also said it was "deeply concerned" about the number of foreign prisoners living in the UK awaiting deportation.
Immigration minister Damian Green said "past mistakes" were being dealt with.
The UK Border Agency - responsible for securing the UK border at air, rail and sea ports and migration controls - was set up in 2008 following the then Labour Home Secretary John Reid's 2006 declaration that the Home Office's immigration directorate was "not fit for purpose".
Borders row
The organisation is now being split into two in the wake of a row last year over revelations that hundreds of thousands of people were let into the country without complete checks. The row led to the resignation of the head of the UK Border Force, Brodie Clark.
The UK Border Force, the section of the agency that manages entry to the UK, is to become a separate law-enforcement body reporting directly to the Home Office while the UKBA will be solely responsible for immigration policy work.
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