The backlog of UK immigration cases has reached 500,000 for the first time and could take four decades to clear, according to a report by a Commons select committee.
The total rose from 322,000 in the last quarter of 2012 to 502,000 by the end of the year, an increase of 180,000 cases.
The Commons Home Affairs Select Committee described the number as 'staggering'.
Committee chairman Keith Vaz said: "The backlog of cases has now hit a staggering half a million people. This could fill Wembley Stadium to capacity six times over.
"It has risen by 56% in just three months. 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.
"There should be no more bonuses paid to any senior management at the Home Office until the backlogs are cleared."
The number includes the full range of cases dealt with by immigration authorities, including immigration and visa applications as well as deportation cases.
The figures also show that the number of foreign criminals on the streets has risen to 4,000, and that there are 35,000 asylum cases waiting to be processed and 61,000 cases waiting to be added to government computers.
In its report, the committee said: "The Home Office must clarify the total number of cases in the temporary and permanent migration pool, exactly what the cases are and the maximum length of time that cases in this backlog have been outstanding."
It accused authorities of "massaging" figures to disguise the full extent of the cases, only months after Home Secretary Theresa May abolished the UK Border Agency (UKBA), declaring it "closed, secretive and defensive". She replaced the UKBA with two other offices under the control of ministers in the Home Office in March.
The report highlighted that spending on consultants by immigration authorities had risen almost twentyfold in the last three months of 2012, to £500,000, and despite having a substantial number of his responsibilites removed, the salary of UKBA chief Rob Whiteman remained at £175,000 a year.
"It should be borne in mind that this is £32,500 more than the Prime Minister's salary," said the report.
"The Home Office must clarify what Mr Whiteman's new roles and responsibilities are.
"The remuneration bill for senior directors has quadrupled to an estimated £700,000.
"If people at the top are not replaced, this will only be an exercise in rebranding, as has happened in previous reincarnations."
Mark Harper, the immigration minister, said: "The UKBA was a troubled organisation for many years, which is why the Home Secretary took the decision to split the agency.
"It will take a long time to clear the backlogs we inherited - but through the changes we have made we are in a much stronger position to do so."
However, the statement offered no explanation of why the backlog had increased so substantially under the current government.
Chris Bryant MP, the shadow immigration minister, said: "Today's report gives a truly damning verdict on the recent performance of the UKBA.
"The backlog, which ministers swore blind they would clear by Christmas last year, has reached over 500,000. This is a worrying indictment of the Home Secretary's priorities."
Sir Andrew Green, chairman of campaign group MigrationWatch UK, said: "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."