Home Office minister Tony McNulty conceded that people might be identified inaccurately on the basis of a test against any one of the biometric checks which the cards will employ. That was why the system would employ 13 biometric features in all.
Mr McNulty even suggested that people with brown eyes could experience difficulties. Interviewed on the World this Weekend on BBC Radio 4, Mr McNulty was asked about a newspaper report suggesting that one in 1,000 people could be identified incorrectly by the hi-tech scans.
He responded: "Inaccurately identified on one of the biometrics ... If there are difficulties with the facial biometric, there are 12 other biometrics (two iris checks and 10 finger and thumb prints)."
Mr McNulty conceded: "There are difficulties with the technology, not least in terms of people who have difficulties with their eyes anyway, not least with people with brown eyes rather than other coloured eyes, and all those are being factored into the equation.
"None of these problems are new, but increasingly as biometrics are more and more used...we think the technology can only get better and better and better."
The Government is planning to use face, iris and fingerprint scans to identify people on ID cards. But studies have found that being scanned in the wrong type of light or in shadow could lead to an inaccurate identification.
The Independent on Sunday reported that internal reports for the Government warned that manual labourers whose fingerprints are worn or nicked could find their fingerprints are not recognised. Men who go bald risk being identified as someone else. Pianists, guitarists and typists - whose fingerprints can be worn down - could also face inaccurate readings.
The paper said that Government trials had also demonstrated that the biometrics of black, elderly and disabled people have a higher chance of being incorrectly matched.
The Commons will vote on whether to give the Identity Cards Bill its Third Reading on Tuesday, and some Labour MP's are expected to oppose the measure. Asked whether he was expecting a significant rebellion, Mr McNulty said. "I have no idea. We are very, very clear though that the arguments have been made, they have shifted away from civil liberties to practicalities and costs and those are the issues we must address as the thing unfolds."
