There are still 11,000 asylum-seekers in the UK who have been waiting for at least seven years to be told if they can stay in the country, a group of MPs has said, as immigration officials fail to get to grips with long-standing backlogs of claims.
The Home Office has still not resolved some 29,000 asylum applications dating back to at least 2007, of which 11,000 have not even received an initial decision on their claim, the Public Accounts Committee (PAC) said.
In addition, the Committee found that the department was also struggling with fresh asylum claims, which is creating a new backlog of cases awaiting an initial decision.
PAC chair Margaret Hodge said: "The pressure is on, and the Home Office must take urgent steps to sort out this immigration mess."
It comes as Nick Boles, the skills minister, admitted Britain does not have control over immigration and may never be able to stem movement from within the European Union.
The Conservative MP said the UK will see a "very large amount of immigration every year" for as long as it remains a leading economy.
"I will always make the argument that we should, for cultural, economic, justice and equality reasons, always have a reasonable level of immigration," he told Total Politics.
"It will always be the position the British people would arrive at if they feel they have control over immigration.
"You can win that argument but only if people know that they, through their Parliament, are in control. The difficulty that has arisen is this sense that we don't have that control - and, bluntly, they're right. It's true."
The Home Office scrapped the UK Border Agency (UKBA) in March 2013 - partly because its performance in dealing with backlog cases was not good enough - and passed operations to three directorates, UK Visas and Immigration, Immigration Enforcement and Border Force.
These three directorates collectively spend some £1.8 billion per year, the PAC report said.
In 2012, the Department set up an "Older Live Cases Unit" to deal with some 400,000 asylum and migration claims dating back to before March 2007 that were still in the system.
This caseload was reduced to 41,000 cases after a review which removed errors, duplicates and individuals who had already left the country.
The PAC report said this still stands at 29,000 with a "worrying" 11,000 backlog cases where no initial decision had been reached.
The Home Office said it was on track to make a decision on all of these 11,000 cases by the end of this year.
But the department is already missing its new targets for processing fresh asylum claims, the PAC report said, with the number of claims awaiting an initial decision increasing by 70% to 16,273 in the first quarter of 2014, compared to same period last year.
This is partly as a result of a "botched" attempt by the Agency to downgrade staff that resulted in 120 experienced caseworkers leaving, the PAC report said.
The UKBA downgraded asylum caseworkers from Higher Executive Officer (HEO) to Executive Officer (EO), which led to the mass exodus.
The failure of a number of IT projects - including the ill-fated eBorders scheme, which would have introduced exit checks at t he border - has also hit the Department's ability to track people through the immigration system, the Committee said.
Cancelling two major IT projects - the department's case work programme and eBorders programme - has meant that close to £1 billion has been spent and wasted, the PAC added.
Rejected visa applications are recorded in a "migration refusal pool", which has just over 175,000 people awaiting removal from the UK, it said.
But private firm Capita - contracted by the Home Office - discovered in 2012 that 50,000 in the pool could not be contacted.
Refugee Council head of advocacy Lisa Doyle said: "It's extremely concerning that so many people are still waiting for a decision on their asylum claim, years after first applying.
"Behind these statistics are individuals, many of whom will have suffered extreme trauma, forced to live day to day in uncertainty while they await the outcome of what could be a life or death decision.
"While people are in the asylum system they are living in limbo; they are banned from working, can't claim mainstream benefits and are simply unable to begin recovering from their experiences and rebuilding their lives.
"It's very important that the Home Office makes decision in a timely manner, but it's even more important that it gets its decisions right first time. It's vital that people who come here fleeing persecution have access to a fair and effective asylum process."
Yvette Cooper, shadow home secretary, said: "Theresa May was very quick to blame the UKBA, but since she took direct control of the border force and immigration system, we have seen backlogs increase sharply and the admission that the Home Office have no idea how many of the 175,000 failed asylum seekers are still here or where 50,000 failed asylum seekers even are.
"However, the failures don't stop there. David Cameron and Theresa May have failed to deliver on her promise to introduce exit checks, to reduce net migration to the tens of thousands, has cost the taxpayer £1 billion on failed IT projects and as the report says introduced no processes to rectify these and other failings."
Dia Chakravarty, political director of the TaxPayers' Alliance, said: "The dramatic mismanagement of the Border Force has left an almighty mess for the Home Office to clear up, but the Department appears to be making it worse.
"These delays not only have a human cost, with asylum seekers forced to put their lives on hold for years on end, but it's clear from the report that botched IT projects and the length of these cases are costing taxpayers too. The Home Office must make addressing this fiasco a priority."
Immigration and Security Minister James Brokenshire said: "The immigration system we inherited was totally dysfunctional with systematic abuse of family, work and student visas and an agency overseeing it all that was completely incapable of the task.
"UKBA was a failing organisation that could not deliver an efficient immigration system for Britain. This is why we split it up into three separate divisions to improve focus on their specific roles in delivering a controlled immigration system and bring them under the direct supervision of ministers.
"Turning around years of mismanagement has taken time, but it is now well under way. We have reformed visa routes to make them more resistant to fraud and cancelled failing contracts; and we are addressing the backlogs we inherited."
Prime Minister David Cameron's official spokesman said the Government was introducing a system of exit checks, to record details of those leaving the country, which would be in place by the end of this Parliament in May 2015.
Asked why it had not been introduced earlier, the spokesman said: "In order to enable the system of entry and exit checks, you need extensive investment in the systems. If that had been put under way in previous parliaments, we would be in a different place."
The spokesman said the Government was continuing to work towards Mr Cameron's target of reducing annual net immigration below 100,000 by next May, despite recent official figures showing it has risen by 68,000 to 243,000.
"That is the objective that has been set out and we are continuing to work towards," said the spokesman.