Courtesy Sky News

The backlog of immigration cases hits 500,000 and the number of foreign offenders waiting to be deported is rising, MPs warn.

Britain's "troubled" border service is backlogged with over 500,000 cases and at the current rate of progress will take nearly four decades to clear, according to a group of MPs.

A rise in the number of foreign-national offenders living in the community as they await deportation was also discovered by the Home Affairs Select Committee in its latest report into the work of the now-defunct UK Border Agency (UKBA).

The committee warned that a recent move to scrap the agency and replace it with two new divisions - one in charge of immigration and visas, the other with border enforcement - was in danger of being an "exercise in rebranding".

It discovered that in the final quarter of last year, spending on external consultants at the agency rocketed from £27,000 in the previous three months to more than £500,000.

"The backlog of cases has now hit a staggering half a million people. This could fill Wembley Stadium to capacity six times over," committee chairman Keith Vaz MP said.

"At the current rate it will take 37 years to clear and the Home Office cannot confirm that this is the last of the backlogs."

After a raft of damning reports, Home Secretary Theresa May abolished the UKBA and replaced it with UK Visas and Immigration and an Immigration Enforcement command, which were brought back under the control of ministers.

Lunar House, the headquarters of the UK Border Agency
The border service was recently split into two divisions
The new head of the UK Visas and Immigration section, director general Sarah Rapson, recently told the committee that Britain's immigration service will never be completely fixed.

The total number of cases in the migration backlog has reached 502,462, the committee said, compared with 321,726 in its previous report.

A total of 4,102 foreign-national offenders were living in the community awaiting deportation in the final three months of 2012, an increase of 122 on the previous three months. Some 65% of these cases are more than two years old.

The committee discovered that the length of time taken to deport an a foreign-national offender has increased by nine days in the same period to 127 days.

Sir Andrew Green, chairman of campaigner group Migration Watch UK, said: "The Government inherited a system in chaos.

"There have been signs of improvement but this new backlog of half a million cases is surely a wake-up call.

"The immigration system is struggling again and must be allocated substantially greater resources commensurate to the scale of the task and the importance the public attach to bringing immigration under control. The policy is now right but it cannot be implemented on peanuts."