AIRPORT face scanners designed to stop terrorists getting into the UK have been “rigged” to cut passenger queues and are creating an “unacceptable” security risk, a confidential Whitehall e-mail has claimed.

UK border officials at Manchester airport allege the machines have been recalibrated so that passengers shown as having just a 30% likeness to their passport photographs are being let into the country.

The devices are designed to check the faces of British and European passengers against their digital passports.

The machines started to throw up numerous false alarms because the software failed to match the faces of law-abiding passengers with pictures on their passports as they stood in the booths.

Officials say the congestion was threatening to derail the introduction of the face recognition scanners, which are central to plans by Jacqui Smith, the home secretary, to make Britain more secure from terrorists, criminals and illegal immigrants.

This weekend Rob Jenkins, one of Britain’s leading authorities on facial recognition, said such a reduction in the matching threshold would make the machines unable to distinguish between Osama Bin Laden and Winona Ryder, the Hollywood actress.

Announcing a trial of five of the devices at Manchester airport last August, Smith said they would improve security by making it more difficult for terrorists using false passports.

Because of the growing number of “false negatives”, immigration officers say they were ordered last month to recalibrate the machines, lowering the match threshold from 80% to 30%.

One official warned in the e-mail: “Update on the calibration – the facial recognition booths are letting passengers through at 30%.

“Changes appear to have been made without any explanation [or] giving anyone a reason for the machines [creating] what is in effect a 70% error rate . . . [The fact that] the machines do not operate at 100% is unacceptable.

“In addition it would be interesting to know why the acceptance level has been allowed to decrease.”

Jenkins, a facial recognition expert at Glasgow University’s psychology department, said lowering the match level to just 30% would make the system almost worthless.

Using facial recognition software employed at Sydney airport in Australia, he found that even people of strikingly different appearance, such as Kevin Spacey and Winona Ryder, the Hollywood stars, showed a match of well above 30% with Osama Bin Laden. Gordon Brown was assessed as bearing even more similarity to Mel Gibson, the actor.

Ministers had hoped the machines would increase the flow of people through airport immigration controls.

The five machines at Manchester’s terminal 1 concentrate on higher-risk flights and passengers. About 80,000

people pass through the terminal every day.

Almost all nonEuropean Union citizens will be tracked in and out of Britain by the end of 2010.

Patrick Mercer, chairman of the House of Commons subcommittee on counter-terrorism, said he would be asking the UK Borders agency about the warnings.

The Home Office said: “We can categorically confirm the gates are making the same high level of checks as when the trials began last August.”

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