The civil servant at the heart of a Whitehall leak investigation was in hiding last night as a political storm raged over the arrest of the Tory frontbencher Damian Green.

The 26-year-old civil servant was detained at his home in Middlesex at 6am on November 19. The assistant private secretary, who has been suspended from his job, is being looked after by the Home Office at a secret location because it owes him a “duty of care”, officials said.

Gordon Brown distanced the Government from the subsequent arrest of Mr Green and the raids on his home, constituency and Commons offices, insisting that this was a police decision.

Senior politicians from all parties, including Michael Howard and David Blunkett, lined up to criticise the action as “overkill”.

Conservative sources last night admitted that the official had asked Mr Green, the Shadow Immigration Minister, for a job but said that he had been turned down and that no inducements had been offered in exchange for any information.

Sir David Normington, permanent secretary at the Home Office, sought to protect Jacqui Smith, the Home Secretary, by insisting that no ministers had been involved in the decision to seek police help over the leaks or in the subsequent inquiry.

In a statement, Sir David, the senior civil servant in the Home Office, said that ministers were told of the arrest of the suspected leaker after it had happened and that they had not known in advance that Mr Green was under suspicion.

Sir David said that he had asked the Cabinet Office to call in the police because a series of leaks were “undermining the effective operation of my department”.

“I was subsequently told that an arrest had been made. Ministers were not involved in the decision to seek police assistance or in the subsequent investigation and were told of the arrest only after it had happened. This is an ongoing police investigation so it would be inappropriate to comment any further,” he said.

In an answer to questions from Dominic Grieve, the Shadow Home Secretary, an official said that Ms Smith had been “kept updated” on the progress of the police investigation.

Conservative anger at the police raid on Mr Green’s property was fuelled by an account given by his wife, Alicia Collinson.

Ms Collinson told friends that nine police officers — some from the counter-terrorist unit — combed through personal effects wearing rubber gloves.

The couple’s 15-year-old daughter, Verity, burst into tears when she arrived at the family’s home in West London after school, she said. Ms Collinson, a barrister, prevented the removal of the family computer on the ground that it contained privileged legal information.

MPs are set to question Michael Martin, the Speaker of the House, over why police were allowed to raid a parliamentary office.

Footage of the raid — filmed by the Tories — is said to include angry exchanges after officers said that Mr Green’s office had become a “crime scene”.

The Home Affairs Select Committee will examine whether the police had the power to go through an MP’s files in Parliament.

Keith Vaz, the committee chairman, said: “I and colleagues are concerned at the implications of a Member of Parliament’s office being searched within the precincts of the Palace of Westminster.”

The suspended official is an assistant private secretary who had worked in the private offices of a number of ministers in the department. It is understood that he was identified as the alleged source of the leaks after a rigorous examination of the paper trail involving the documents.

Mr Green was arrested on suspicion of aiding, abetting, counselling or procuring misconduct in public office. The case is likely to turn on whether there is evidence that Mr Green asked for specific leaks.

Whitehall unease over leaks intensified this week when details of the Pre-Budget Report were leaked before Monday’s announcements. Treasury officials last night refused to say whether the police had been asked to investigate.

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