Almost 4000 foreign criminals whom the Government wants to deport are at large in the community, it has been revealed.

Some 2500 were released from jail more than two years ago and more than 800 have been free for more than five years, UK Border Agency (UKBA) statistics showed.

Rob Whiteman, UKBA's chief executive, admitted foreign offenders were not deported quickly enough.

He blamed delays on the length of time it can take for cases to go through the system, the multiple rights of appeal on different points of law, difficulties obtaining documents from foreign countries and problems with people trying to obstruct the system.

Some case law which puts the interests of children above the interests of deportation can also cause difficulties, he said.

One foreign criminal frustrated attempts to deport him nine times before he was sent back earlier this year, Mr Whiteman told MPs on the Commons Home Affairs Select Committee.

A trick used by offenders is to tell officials on arriving home that they are not from that country, he added.

Mr Whiteman said: "We do not want foreign national offenders to be in the community for several years before they are deported."

But he claimed that in 90% of cases courts had ruled the criminals should be released because there was no realistic prospect of a quick removal.

"Our view is that they should be held in detention," he said.

About 3900 foreign national offenders who are subject to deportation action were living in the community as of April 4, the UKBA figures showed.

These include 817 offenders who were released more than five years ago, 1650 who were released more than two years ago, and 664 who were released between one and two years ago, according to a breakdown given in a letter from Mr Whiteman to MPs.

A further 31 were released between six months and a year ago and 327 were released within the previous six months. There were "data quality issues" with another 166 cases.

The 3900 foreign offenders living in the community are all on bail, the Home Office said.