British Members of Parliament have condemned the UK Border Agency (UKBA) for failing to address its growing backlog of immigration cases involving foreign nationals who should have been removed from the country.

The MPs' report maintains that there are more than 275,000 migrants residing in the UK who are slated for removal.

Labour MP Keith Vaz told the BBC that the number of backlogged cases was now equivalent to the entire population of Newcastle upon Tyne, a city in northeast England.

It's easy [for migrants] to get in [to Great Britain], but near impossible to keep track of anyone, let alone get them out, he explained.

Furthermore, bonuses for UKBA officials had gotten out of hand and did not appear to be linked to performance. Senior agency officials were awarded about US$5.4 billion in 2010 alone, said Vaz, adding that the money should have been used to hire more caseworkers instead.

Catching up on backlogged cases could take years. MPs recommend that the UKBA form a special committee to further investigate its failure to keep up with its caseload.

This outcry is just one of a series of similar reports from parliamentary officials. In October of last year, a group of MPs released a study finding that the UK Border Agency had allowed too many migrants to remain in the country on human rights grounds, often contradicting decisions made by national courts.

In December, the agency was accused of losing track of the whereabouts of thousands of foreign offenders. And in April of this year, MPs said that the UKBA had an overwhelming backlog of cases that were full of inconsistent data.

So Monday's report evinces an ongoing struggle, not a new problem. Improvements have been made, the UKBA was quick to point out. On spokesman told the BBC that the backlog of cases was being addressed.

Over 2,000 over-stayers 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, he said.

But the outstanding problems are daunting. The UK has long been trying to close the so-called 'Lille loophole,' for instance, but has come up against resistance from Belgium and France.

Under the Schengen agreement, borderless travel is allowed between most countries in Western Europe; the UK is not included. But by boarding a Eurostar train from Brussels, Belgium, to Lille, France, which then happens to go on to a final destination in London, migrants essentially have a loophole that allows them to cross the English Channel without acquiring the necessary passport or visa.

Furthermore, the UKBA has documents on migrants whose removal is on hold due to the fact that no information into the migrants' whereabouts can be found. Tens of thousands of these cases remain on file.

To further complicate matters, the government isn't the only group leveling strong criticism against the UKBA. A group of the agency's own disgruntled staffers are planning a strike for July 26, in protest of the organization's policies regarding worker salaries and the increasing privatization of services. The timing is especially worrisome, as July 27 marks the opening ceremony of the Olympic Games, and international travel is expected to be particularly heavy.

Border security is of the utmost concern in the lead-up to the games, so the UKBA will face an especially daunting workload over the next couple of weeks.