THE crisis-hit UK Border Agency (UKBA) has a backlog of 275,000 cases including missing foreign criminals, failed asylum seekers and illegal immigrants, according to a damning report by MPs.

The UKBA's reputation is suffering a further blow with the publication today of a report by the House of Commons Home Affairs Select Committee. It is still processing enough cases to populate Newcastle-upon-Tyne.

The list includes 150,000 migrants who have been refused permission to stay in the UK but who may still be in the country illegally, 21,000 asylum cases, and 3900 foreign offenders living in the community.

Another 57 foreign criminals who were released in 2006 without being considered for deportation have not been traced.

It comes as public-sector union members prepare to go on strike in a dispute over job cuts and pay on Thursday, the day before the start of the Olympics.

The dispute threatens to disrupt airports such as Heathrow, where the majority of spectators will be flying in, and Edinburgh as it gears up for the start of the festival next week.

Chairman Keith Vaz MP warned the backlog would take years to clear, adding that the agency seemed to have "acquired its own Bermuda triangle".

He said: "It's easy to get in [to the UK], but near impossible to keep track of anyone, let alone get them out."

The study is the first time committee has collated all the outstanding cases at the agency. He added: "This backlog is now equivalent to the entire population of Newcastle-upon-Tyne."

The report said MPs did not believe the Government's aim of cutting the 260,000 student visas issued each year by one-quarter would benefit the UK.

Students should be excluded from the net migration figures instead, the politicians added.

Britain would then continue to attract international students, a market worth £7.9 billion, and still be able to aim to meet Prime Minister David Cameron's pledge to cut net migration from 250,000 to tens of thousands by 2015, the report said.

Mr Vaz added: "This will enable the Government to encourage students to come to the UK whilst maintaining their position on curbing immigration."

University chancellors have urged Mr Cameron to class international students as temporary rather than permanent migrants, but immigration minister Damian Green said students staying for more than a year were not visitors.

The report examined the agency's work between December and March and called for it to make all its inspections of colleges unannounced, rather than giving them advance notice.

The report found the archive used for cases where the agency has lost track of the applicant contained 80,000 asylum and 21,500 immigration cases.

The agency "does not have a strong record in deporting foreign national offenders" and should set up a team to examine why foreign criminals living in the community had not been deported, the MPs said. They added that in future, deportation proceedings should begin as soon as a prisoner is sentenced.

A Home Office spokesman said: "Over 2000 overstayers have recently been removed following targeted enforcement activity, foreign national offenders are being removed more quickly and we are performing well against visa processing targets.

"Talented students are welcome in the UK, but we have introduced new powers to toughen up the system."

The agency is expected to face more negative headlines if a strike by 16,000 members of the Public and Commercial Services Union (PCS) goes ahead.

Staff at the Home Office, along with the Identity and Passport Service and Criminal Records Bureau, could take part. The Home Office has had to bring in 10,000 soldiers to beef up security at the Olympics after G4S's failure to fulfil its contract. But the dispute over plans to cut 8500 jobs and cap a pay rise at 1% has been condemned by political leaders.