The decision of the UK Borders Agency (UKBA) to allow 160,000 asylum seekers to remain in the UK has sparked controversy.
A home affairs committee report questioned the role of the UKBA and suggested that in effect an amnesty has taken place.
This is despite David Cameron stating during last year's election campaign that no amnesty would be available for illegal immigrants.
Around 450,000 cases have formed a backlog which is yet to be cleared. In 75,000 of these cases the applicants cannot be found and it is not known whether they remain in the UK.