Nearly 1,500 foreign prisoners are being held in British jails beyond the term of their sentence.
A total of 547 foreign offenders are being held in prisons after their sentences have ended, while a further 919 are in immigration removal centres, immigration minister Mark Harper revealed.
Mr Harper, who was responding to a parliamentary question by Conservative MP Priti Patel, could not confirm how long the prisoners had been held.
Prime Minister David Cameron pledged nearly two years ago to put an end to agreements that mean foreign offenders cannot be returned home without their consent.
In April 2010, there were 701 foreign offenders detailed in jail after their sentence, which fell to 516 in April 2011 but rose again to 552 in the same month in 2012, the figures revealed.
The number of people held in immigration detention centres after completing a prison sentence has fallen from 1,213 in April 2010 to 812 in April 2012.
A UK Border Agency spokesman said: "We will always detain foreign criminals awaiting deportation if they pose a risk to the public.
"Those who abuse the privilege of coming to the UK by breaking our laws should be removed at the earliest opportunity and we are speeding up the deportation process.
"Deportation can be delayed for many reasons, including human rights challenges and a lack of co-operation by the offender. This can lengthen the period of time an individual spends in immigration detention."