Sensitive details of race, religion or political views could eventually be included in the Government's planned 'entitlement cards', the information watchdog warned yesterday.
Critics have complained that the proposed cards, which would be carried voluntarily, could pave the way to compulsory identity cards. Richard Thomas, the Information Commissioner, said he had "serious concerns" over whether the cards would infringe privacy and data protection laws. He said: "Identity cards may be OK, but where do you draw the line? How do you stop it being a requirement to hold a card in public? How do you stop it being a requirement, for example, of sensitive data ... racial background or religion or political views all that being held by the state?"
He told BBC Radio 4's Today programme: "I do have anxieties about a monolithic state system having so much information on every single citizen in this country."
He delivered his warning as a consultation period on how the cards might be introduced nears its end. David Blunkett, the Home Secretary, supports their use, but other Ministers are much more wary.
Mr Thomas said a massive database of information would be needed to run a scheme that could hold information on nearly 60 million people. The task of keeping it accurate and up-to-date would be enormous.
He also raised fears that the cards the most ambitious undertaken by any country could be targeted by fraudsters.
He called for an independent body to administer any scheme, strict limits on the amount of information cards could hold and stronger data protection.
However, Andy Burnham, the Labour MP for Leigh and a strong supporter of ID cards, said: "I honestly see simple benefits that outweigh some of the negatives he has talked about. We live in an increasingly uncertain world and people use ID fraud or conceal their identity for a whole range of negative reasons.
"I believe, having given this issue careful thought actually, I have come to the conclusion that an identity card would be in the interests of a majority of people who carry their identity anyway day in, day out."
The Home Office said it would study Mr Thomas's comments carefully.