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Michael Martin, Speaker of the Commons, tried to deflect the blame today in a bitter political row over the police search of a Tory frontbencher's Commons office.

In a much-anticipated statement to MPs, Mr Martin announced that the detectives who searched the offices of Damian Green, the Shadow Immigration minister, last week did so without a warrant.

Mr Martin appeared to lay most of the blame on Jill Pay, who as Serjeant-at-Arms is the Commons officer responsible for policing. To his "regret", he said, Ms Pay had signed a consent form allowing the officers to search the office.

But he also accused Scotland Yard of not following the proper procedure because the officers in question did not make it clear - "as they are required to do" - that Ms Pay could have insisted on a search warrant. The Prime Minister refused to say whether he regretted the fact that a warrant had not be sought - adding that it was for a parliamentary and police inquiry to decide.

Mr Green was held for nine hours last Thursday and questioned after being arrested as part of a criminal inquiry into Home Office leaks. While he was being held, police searched his home and constituency offices and his office at Westminster.

Attempting to defuse Opposition anger, Mr Martin announced an independent review of the case by seven "senior and experienced" MPs and a Commons debate. He also promised that, in future, police would need a warrant to execute any searches in the Palace of Westminster.

"I must make it clear to the House that I was not asked the question of whether consent should be given or whether a warrant should have been insisted on," he said. "I did not personally authorise the search."

He added: "I have reviewed the handling of this matter. From now a warrant will always be required."

Mr Green was held for nine hours last Thursday and questioned after being arrested for aiding and abetting misconduct in a public office.

Tory sources say that detectives accused him of "grooming" a young Home Office official, Christopher Galley, who has admitted responsibility for the leaks, which he says were in the public interest.

While Mr Green was being held, police searched his constituency office in Ashford, Kent, and his Commons office. MPs from all parties were angered both by his treatment and by the decision to let the officers into the Palace of Westminster, seeing it as a breach of parliamentary privilege.

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