Downing Street today promised safeguards to prevent the development of a Big Brother society in which government has large secret files on everyone in Britain.

A No 10 spokesman said there would be a watchdog to prevent situations in which personal information gathered by one Whitehall department was made indiscriminately available to other civil servants without the individual's knowledge.

Downing Street was responding to warnings issued by Richard Thomas, the Information Commissioner, that Government plans for huge centralised databases on all its citizens, such as the proposed biometric identity cards, meant that Britain risked "sleepwalking into a surveillance society".

He told The Times that the Government should define exactly what identity cards were for.

But a No 10 spokeswoman said today that information gathered for one purpose would not be misused for another.

"We have made it clear that there are going to be guarantees about function creep," she said.

"That is not what is going to happen. There is going to be proper oversight."

Mr Thomas is the watchdog responsible for ensuring that the Government does not misuse personal information about its citizens.

He singled out three projects of particular concern: David Blunkett's identity card scheme; a population register planned by the Office for National Statistics; and proposals for a database of every child from birth to the age of 18.

He said: "My anxiety is that we don't sleepwalk into a surveillance society where much more information is collected about people, accessible to far more people shared across many more boundaries than British society would feel comfortable with."

Asked if he thinks there is a risk of this occurring because of the Government's plans, Mr Thomas tells The Times: "I think there is a danger, yes."

Hazel Blears, a Home Office minister, rejected Mr Thomas's concerns today. "I don’t think we are sleepwalking anywhere," she told Sky News.

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