An investigation into UK border controls has revealed that more than 16,000 immigrants are waiting to hear whether they can stay in Britain.
The number of applicants is growing at a rate of 700 a month, with around 14,000 already refused the right to stay.
Independent Chief Inspector for Borders and Immigration John Vine discovered the backlogs as part of an inquiry into applications to remain in Britain on the basis of marriage.
Mr Vine said: "We are concerned that this backlog of cases has been allowed to develop. As a result, some applicants have been waiting for considerable periods of time for their cases to be resolved."
Thirty-one stowaways had their hopes of entering the UK shattered after border officials found them hidden inside four UK-bound lorries at the Port of Calais.
A sniffer dog indicated there were people inside a Peterborough-bound Turkish-registered lorry and 12 Albanians were found among the cargo.
Officers using heartbeat monitors also discovered six Afghans hidden in a Polish-registered vehicle which was heading to Accrington, Lancashire, with its load of sofas.
A detector dog also led officers to find six Albanians hidden among nappies on a Czech-registered lorry bound for Lincolnshire.
The fourth discovery was in an Irish-registered lorry heading to the Republic of Ireland. A dog led officers to find seven people on board - three from Iran, two from Pakistan, one from Afghanistan and a Syrian.
All the stowaways were handed over to French border police.
The damning report follows comments by the chairman of the Home Affairs Select Committee, Keith Vaz, earlier this month.
Mr Vaz said the number of unresolved cases that UKBA is dealing with - more than 300,000 - is "spiralling out of control".
He said: "There are now about the same number of cases awaiting resolution by UKBA as there are people living in Iceland."
Chief inspector of the UK Border Agency John Vine has made the following recommendations to the UK Border Agency:
- Routine checks against police records.
- Ensuring that accurate information is given to the Home Affairs Select Committee.
- Making a public commitment to resolve the backlog within a certain timeframe
Chief inspector of the UK Border Agency John Vine was asked to evaluate how well UKBA had handled the backlog of thousands of unresolved immigration cases.
Mr Vine said he believed little had been done to try to resolve the cases before they were passed over.
He said: "Through the inefficiency and delay of the agency, those who would otherwise have faced removal will have accrued rights to remain in the UK."
Mr Vine also criticised "poor" customer service, and said that a lack of resources meant that deadlines were often missed, even when legal action was threatened.
The report said: "The issue of limited resources also created a significant impediment to case clearance.
"As a result, timescales given to applicants or their representatives about the resolution of cases were frequently missed, even where litigation was being threatened."
- UK Border Agency (UKBA) staff dealt with a backlog of immigration cases so inefficiently that at one point 100,000 pieces of post were unopened.
- In March 2011, there were 147,000 unfinished cases that were passed to an audit unit tasked with dealing with the backlog.
- More than 150 boxes of post, including letters from applicants, MPs and lawyers, lay unopened.
- In a sample of 135 files examined as part of the inspection, each case had lain dormant for an average of 87 months before they were reopened in 2010 for consideration.
- The shortest period of inactivity was six months and the longest period of inactivity was 17 years and nine months.
- A total of 115 cases were found to have entered the UK illegally, and there were only 10 cases where active efforts had been made to trace absconders.
UK Border Agency (UKBA) staff dealt with a backlog of immigration cases so inefficiently that at one point 100,000 pieces of post were unopened, a report said today.
Chief Inspector of Borders and Immigration John Vine found that security checks were not properly carried out on old cases and that workers had failed to check the records of other Government departments.
Applications were placed into an archive of unresolved cases after "very minimal work", despite the agency assuring MPs that "exhaustive" checks had been carried out, he concluded.
The number of outstanding immigration and asylum cases rose by 25,000 in three months and is "spiralling out of control", making the total caseload the equivalent of the population of Iceland, the Commons Home Affairs Select Committee Chairman Keith Vaz has said.
More than 300,000 cases needed to be dealt with at the end of June, up 9% over the previous three months, the Commons Home Affairs Select Committee revealed.
But clearing the backlog should not be a rushed job done without the proper checks, the committee's report on the UK Border Agency (UKBA) warned.