Identity cards would increase the danger of personal information being stolen and used for fraudulent purposes, according to a new watchdog.

Information commissioner Richard Thomas said he was extremely anxious that there was a real risk people's identities would be stolen.

If I can coin the phrase 'function creep' that is my greatest anxiety Richard Thomas

A simple entitlement card that included the name, address and date of birth would be a convenient way for people to establish their identity and access public services, he said.

But if the remit was extended to include details like an individual's religious or racial background or work information then Mr Thomas said he would have concerns.

He told the Guardian: "That sort of information the government says will not be there.

"If it starts to be there then I start having increasing anxieties.

"If I can coin the phrase 'function creep' that is my greatest anxiety."

Mr Thomas added that he was asking for guarantees that a "future administration won't bolt on to the infrastructure now being laid down and start to extend the scheme".

Mr Thomas' new job replaces that of the old data protection registrar.

10 year plan?

He wants a promise that ministers will hold a further debate in Parliament before an extension of the role of the proposed "entitlement" cards.

Government proposals for a universal system of entitlements could take as many as 10 years to implement.

Under the plans, it would not be compulsory to carry the entitlement card.

Those in favour believe it would ultimately reduce bureaucracy by removing many of the occasions on which people have to prove who they are.