Michael Martin, the Speaker of the House of Commons, appeared increasingly isolated last night after ministers questioned the decision to allow police to raid the Commons office of Damian Green.

Harriet Harman, the Leader of the House, called for a review of the right of police to search Commons offices as David Davis, the former Shadow Home Secretary, prepared to lead protests after the Queen’s Speech on Wednesday.

In the first acknowledgement of the scale of the political fallout from the case for the Government, Ms Harman said she was “very concerned” about the police action.

She questioned the nature of the warrant used by police to raid a parliamentary office and complained that she should have been informed by the Commons authorities. Concerns that parliamentary privilege had been breached needed to be properly investigated, she said.

“I think the Speaker might well want to review the processes by which authorisation is given to search the Palace of Westminster,” she said yesterday. “We have got to be sure that whilst MPs are not above the law, that they are able to get on with their job without unwarranted interference by the law. These are very, very big constitutional principles, we have to make sure they are protected.”

The Speaker’s official spokeswoman said that Mr Martin planned to make a statement to MPs about his role as soon after the State Opening of Parliament as possible.

Senior MPs from all parties have criticised what they claim was a failure to protect parliamentary privilege and will return to the House of Commons this week determined to reassert their rights. They are particularly concerned at the confiscation of Mr Green’s computers, which would have contained correspondence from his constituents.

Senior Conservatives said that they would be demanding to know whether Mr Martin had personally approved the search of Mr Green’s office.

“We are very concerned to know exactly what his role is in all this. There’s no doubt that the Speaker has questions to answer,” a Conservative Party source said. It was initially reported that Mr Martin was only informed of the decision by Jill Pay, the Serjeant at Arms. MPs believe it is highly unlikely that the Commons official in charge of security would have allowed the search without the Speaker’s approval.

Conservative sources said that the serjeant had informed Patrick McLoughlin, the party’s Chief Whip, that she had allowed the search because the police had told her it had been approved by the Director of Public Prosecutions.

In fact a spokeswoman for the Crown Prosecution Service said that the DPP was simply informed of Mr Green’s impending arrest in line with procedure for all high-profile cases. Dominic Grieve, the Shadow Home Secretary, said it seemed that the police might have deliberately misled Ms Pay.

Mr Grieve’s predecessor put himself at the head of preparations for a crossparty protest when Parliament returns for the new session on Wednesday. Mr Davis said that he would be studying parliamentary procedure to find the most effective way of registering MPs’ anger.

One option was to force a debate on the so-called sessional orders, he said, adding that any protest would take place after the Queen had delivered her opening address.

He suggested that he was ideally suited to co-ordinate any cross-party action. “I don’t think that this is something that can come from the front bench,” he said.

Mr Green is likely to take a prominent position on the Conservative front bench during the debate, although senior sources played down suggestions that he might sit next to David Cameron.

Mr Martin’s spokeswoman said that he would not be answering any questions about his role before Wednesday. “It is right that MPs hear first from the Speaker and that is why he plans to make a statement,” she added.

Ministers claimed that the Conservatives would be wary of forcing Mr Martin to resign from his position since any replacement would almost certainly be another Labour MP.

The key players

Damian Green Conservative immigration spokesman with a safe seat in Kent. He was given the portfolio because his reputation as a moderate would deflect slurs by Labour trying to label him “racist”.

Jacqui Smith First female Home Secretary, appointed by Gordon Brown last year. Former teacher with marginal Midlands seat who entered Parliament in 1997

Sir David Normington Permanent Secretary at the Home Office. Worked with Jacqui Smith as a junior education minister. Brought in to buck up Home Office before it was dismembered months later

Bob Quick Chief Constable of Surrey since 2003, he was made head of the Met’s antiterrorism unit this year. He ordered the raids on Mr Green’s homes and offices

Jill Pay Became first female Serjeant at Arms at the Palace of Westminster in January. She is responsible for security and keeping order in the Commons

Michael Martin Former sheet metal worker and union official from solid Labour seat in Glasgow. Became the first Catholic Speaker since the Reformation in 2000

Christopher Galley Assistant private secretary, suspended after arrest for misconduct in public office by allegedly leaking information to Mr Green

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