Immigration officials are under pressure to hit targets, MPs were told
An estimated 300,000 visas giving foreigners the right to come to Britain may be wrongly approved every year, a committee of MPs has been told.
Linda Costelloe-Baker, the independent visa monitor, told the Home Affairs Committee it was "reasonable" to assume 15% of short-term approvals were wrong.
She also said officials were "under pressure" to issue - rather than reject - visas to meet productivity targets.
The Tories said it made a "mockery" of Labour's claims to control immigration.
Embassies and consulates examine 2.4 million applications each year from tourists, business people and those visiting relatives - they check applicants intend to leave after their visa expires and have enough money to live in the country and are not looking for a job, Ms Costelloe-Baker told the committee.
Rejected applications were checked for accuracy but there was not a similar system in place to check applications that were approved, said Ms Costelloe-Baker.
"About 80% of visas are issued and yet there has been no external scrutiny over that 80%."
Officials considering visa applications found it much easier to approve visas than reject them, she said because issuing was a "much faster" process than refusal.
"I don't think there has been adequate scrutiny of decisions to issue," she said, adding: "I think there is pressure to issue visas because it helps people hit their productivity targets."
Conservative MP David Davies asked if it was reasonable to assume that, if 15% of rejections were found to be incorrect, a similar proportion of approvals were "incorrectly approved".
"I think that's a reasonable supposition," Ms Costelloe-Baker said, adding that that total would include cases where an applicant rightly got a visa but where there were errors in the way the visa was approved.
Mr Davies continued: "I'm trying to make an assumption here which is reasonable based on the evidence and that is that a large number of visa applications have been incorrectly approved in the country where they were requested."
Ms Costelloe-Baker said: "I think that's a reasonable assumption."
But she said entry clearance officers were also conscious of the scrutiny their decisions were liable to come under when people applied for leave to remain when their visas expired.
She said there was evidence the new points-based system, which comes into effect on 27 November, would be more effective, although it was too early to tell.
Based upon a visit to the British embassy in Tehran, she said: "The quality of decision making and refusal notices there was poor but the quality of work on the points-based system was excellent and that is because it's a much clearer, simpler system."
But shadow home secretary Dominic Grieve said her comments highlighted a major flaw in Labour's immigration system.
"This makes a mockery of Labour's claims to have a grip on our immigration system. It is obvious that its operation is neither firm, nor fair.
"This error rate not only increases the scope for increased illegal immigration, but is obviously a security threat.
"The public will be dismayed that Labour targets are making our border controls more vulnerable."
Ms Costelloe-Baker's role as the independent monitor of visa entry is being phased out and she will be replaced by a new chief inspector of the UK Borders Agency, John Vine, former chief constable of Tayside Police.
Mark Sedwill, the international director of the UK Border Agency, said: "Our decisions are fair and objective, and last year the Independent Monitor determined they were right and reasonable in 99% of cases.
"It is untrue to claim our staff give out visas when people do not meet the criteria set out in the immigration rules.
"In fact every application is scrutinised, fingerprints are taken, and the individuals checked against a range of watch-lists. Visas provide the first line of defence against those who seek to abuse the system. Travellers are subject to further tough checks at the border.
"Already we've fingerprinted more than three million people and identified 4,600 cases of identity fraud. So far this year we've refused visas to nearly 20% of applicants."
The Office for National Statistics is due to publish its net migration figures - showing the numbers entering and leaving the UK - on Wednesday.