Has Mr Speaker lost the confidence of the House?

The findings of a poll of backbench MPs were set to trigger a parliamentary revolt, after more than one in three respondents said they no longer had confidence in Glasgow MP Mr Martin in the wake of the Damian Green affair.

One former deputy speaker called on Mr Martin to announce plans to retire next year, while Tory leader David Cameron refused to say he had confidence in the Speaker. With MPs disregarding parliamentary convention by openly discussing Mr Martin's future, the scene was being set for what appears to be the first enforced removal of a Speaker.

Ahead of a Commons debate today on the fallout from the arrest of Mr Green on 27 November, a BBC survey found 32 of 90 MPs prepared to discuss the Speaker's future no longer retained confidence in his ability to protect the independence of the Commons.

These included eight Labour MPs, 14 Tories and seven Liberal Democrats. Another 50 considered the Speaker "culpable" for the raid.

At least three MPs have already called on Mr Martin, who has been dogged by controversy since becoming Speaker in 2000, to quit. But yesterday's poll prompted several high-profile politicians to add their voices to growing uncertainty about his chances of survival.

Temperatures were further raised by a newspaper report suggesting Mr Martin was determined to remain Speaker after the next general election – a story his spokeswoman then downplayed.

Shadow home secretary Dominic Grieve said: "That (another term] is a matter for MPs to decide, not for the Speaker to decide."

Tory peer Lord Naseby, who was a deputy speaker under the popular previous speaker, Betty Boothroyd, said Mr Martin had made a "very big mistake" by failing to block the police raid and should retire next year to allow a new speaker to get to grips with the role before the next general election.

Lord Naseby, the former Tory MP Michael Morris, said: "Why the Speaker was not in the lead role (over the Green search] is something I find absolutely incomprehensible.

"He needs to reflect on that situation. I don't think it is for the members to necessarily put down a motion of no confidence, because that is a very drastic stage, but he needs to reflect on his position, frankly. In my judgment, he has let the House of Commons down."

Sir Malcolm Rifkind, the former Tory foreign secretary, said he had been "greatly surprised and very, very disturbed" at Mr Martin's role in the Green affair. "I don't think I am being controversial in saying I don't think that Speaker Martin will go down as one of the great speakers of the House of Commons," he said.

Last week, Gordon Brown's spokesman was forced to make clear that the Prime Minister had confidence in Mr Martin after Labour's deputy leader, Harriet Harman, had failed to give him her explicit backing.

Tory leader David Cameron, asked yesterday if he had confidence in the Speaker, was cautious. He said: "I want to have the confidence we should all have in the Speaker's office and the Speaker, and that needs to be put right."

Ministers attempted to sidestep questions about Mr Martin's future, but there was cross-party concern at the fallout from the raid on Mr Green's office.

A government motion that would prevent police from entering parliament without a warrant is due to be debated by MPs today, but the Tories were furious at attempts to delay an internal inquiry until the conclusion of a police probe into the leak of confidential Home Office documents to Mr Green.

Despite calls for MPs to avoid "tribal" party politics, today's debate is shaping up to be an acrimonious battle along party political lines.

In an emergency statement to the Commons last Wednesday, Mr Martin denied authorising the police raid but revealed he had been warned twice by the Serjeant at Arms – the most senior security official in the House of Commons – that it was imminent. Many MPs are angry that Mr Martin failed to seek advice on the legality of such a raid.

The backbench rebels first to demand that Mr Martin quit were Labour's Bob Marshall-Andrews, Tory Douglas Carswell and Respect's George Galloway.

Yesterday, Norman Lamb, a Lib-Dem frontbencher, said it was "unfair" that the Speaker had sought to lay the blame at the door of the Serjeant at Arms, Jill Pay.

"It is right to say MPs are reluctant to criticise any speaker, but I couldn't just sit on my hands when a senior member of staff was treated in that way and, ultimately, we become complicit if we remain silent," Mr Lamb told the BBC.

Stephen Ladyman, a former Labour transport minister, said MPs had to put the protection of democracy and the ability of MPs to do their jobs on behalf of constituents ahead of any personal loyalty to Mr Martin. Mr Ladyman said: "It is a serious matter for a member of parliament to lose confidence in the Speaker.

"We will be incredibly distressed if the inquiry throws up evidence of any level of culpability in the Speaker, that he had the opportunity to do something about it but didn't do it."

But Margaret Beckett, the Labour housing minister, accused the Tories of seeking to influence the police inquiry into the Home Office leak. She said: "I genuinely think this is getting close to intimidation of the police."

The Green affair and what happened when

MICHAEL Martin was first informed of the police plan to raid the parliamentary office of a Tory MP on 26 November, the day before it took place.

He was informed of this by the Sergeant at Arms, Jill Pay, effectively the head of security in the Commons. At that stage, neither the Speaker nor Ms Pay knew the identity of the MP in question.

The following morning, Ms Pay was visited by Metropolitan police officers at 7am, given the background to their investigation – they were following a complaint from the top civil servant at the Home Office, Sir David Normington, about the leak of sensitive government information to the Conservatives – and given Damian Green's name.

She called Mr Martin, passed on Mr Green's name, and said a search may be about to take place on the Commons office of the Ashford MP and immigration spokesman.

Mr Martin said last Wednesday that he was not told by Ms Pay that police did not have a warrant. Nor did police explain, as he said they were required to do, that Commons authorities were entitled to refuse access or to insist on a warrant. "I did not personally authorise the search," Mr Martin insisted to MPs.

He said he was only informed on 2 December that Mr Green had been held on suspicion of conspiring to commit misconduct in public office and on suspicion of aiding and abetting misconduct in public office.

But the Speaker's failure to seek legal advice in advance of the raid has caused many MPs to question his judgment.

Removal of a Speaker not in the rulebook

THE removal of a Speaker against his wishes defies modern parliamentary convention as the system is designed to offer as great a protection as possible from government interference.

As the representative of MPs rather than the executive, the Speaker is generally allowed to continue in office until he or she wishes to retire. The alternative is that they die in office, which last happened in 1943.

Parliamentary textbooks are silent on the last occasion a Speaker was forced from office, the normal convention being that the incumbent simply retires from Parliament at a general election. Speakers choosing to retire mid-parliament are immediately elevated to the House of Lords, sparking a by-election.

New procedures for electing the Speaker were agreed in 2001 but have yet to be used. It would involve a secret ballot if there is more than one candidate.

A sitting Speaker would declare in advance of a general election that he or she wished to stand again. That would mean there would be no challenge from a Labour, Tory or Lib-Dem candidate – although in Scotland the SNP has refused to abide by this convention and has challenged Michael Martin.

The most likely way to remove Mr Martin would be a delegation of senior figures led by the Father of the House, the longest-serving MP. But public indications from a sizeable number of MPs – in particular, party leaders – would be enough to force a Speaker to indicate they intend to stand down at or before the next general election.