Gordon Brown has been urged to "get a grip" on data security after it was revealed that Hazel Blears, Westminster's Communities Secretary, had a desktop computer stolen. It supposedly contained sensitive departmental information on extremism.

Gordon Brown has been urged to "get a grip" on data security after it was revealed that Hazel Blears, Westminster's Communities Secretary, had a desktop computer stolen. It supposedly contained sensitive departmental information on extremism.

With the UK Government facing fresh embarrassment following the third security lapse in a week, her spokesman last night confirmed that Ms Blears's aides had breached data security rules by sending official information to her electronically.

Peter Housden, the department's top civil servant, said: "It is clear that papers have been sent to Hazel Blears in a way that is not fully consistent with the departmental guidance." He insisted "no damage had been done" because the documents were not "classified as secret or top secret".

He went on: "In any event, the computer was password-protected. I have instructed my officials that departmental procedures, guidance, and the awareness and accessibility of that guidance are now strengthened to ensure this does not happen again. I take full responsibility for ensuring this is done."

The computer was stolen from the minister's constituency office in Salford on Saturday evening. It was emphasised that it held no personal data.

"The news that a government minister may have been directly responsible for the loss of data relating to extremism is extremely alarming," said Dominic Grieve, the Shadow Home Secretary.

Chris Huhne for the Liberal Democrats said: "This is the third breach of secrecy in a week. The government has to get a grip on the slap-dash culture of sloppiness that threatens national security," he added.

Last week, a Cabinet Office official was suspended and an investigation launched after secret papers featuring details of al Qaeda and security in Iraq were left on a train.

Jacqui Smith, the Home Secretary, is to be hauled before the Commons Home Affairs Committee after plans to tackle funding for global terrorism were also found on a train.