The Speaker of the House of Commons has been challenged by MPs to stand down in unprecedented scenes in the chamber.
Michael Martin did not mention his future in a statement on the expenses furore - instead setting out proposed action to reform the system.
He said he was "profoundly sorry" for his role and said all MPs must accept blame for the "terrible damage" done.
But a succession of MPs challenged him openly, saying they wanted a debate and a vote of no confidence in him.
It follows a week of damaging media revelations about MPs' expenses and criticism of the way Mr Martin has handled the row.
Later on Monday, Lib Dem leader Nick Clegg said he was "minded" to sign a motion of no confidence in the Speaker - backed so far by about 20 MPs - while Tory frontbencher Michael Gove said his constituents were clear Mr Martin must make way.
In a statement to a packed Commons, Mr Martin apologised for the expenses scandal and outlined steps he would be taking ahead of the findings of an independent inquiry into the allowances system, expected in the autumn.
These included asking party leaders to meet him and members of the House of Commons Commission within 48 hours to look at what proposals for reform could be agreed upon and put to MPs for approval.
In the meantime the Glasgow North East MP urged members not to submit expenses claims for approval.
This House should calm itself down, should have a period of reflection
He said: "We all bear a heavy responsibility for the terrible damage to the reputation of this House. We must do everything we possibly can to regain the trust and confidence of the people."
Labour's Gordon Prentice was the first to stand up to ask about the no confidence motion, only to be told it was not a "point of order" - to shouts of "oh yes it is".
Douglas Carswell, the Conservative backbencher who is putting forward the motion, got up to ask when it would be debated and when MPs would be able to choose a new Speaker with "moral authority to clean up Westminster and the legitimacy to lead this House out of the mire".
But he was told it was not a "substantive motion, it's an early day motion", which led to MPs shouting and Mr Martin having to seek clarification from a clerk.
Veteran Labour MP David Winnick asked him, "with some reluctance" to give "some indication" as to when he would retire, saying "your early retirement sir, would help the reputation of the House".
Mr Martin replied that was "not a subject for today".
THE SPEAKER'S ROLE
The Speaker controls the proceedings of the House of Commons, chairing debates, keeping order and calling on MPs to speak
The Speaker is also responsible for the running of much of Parliament - including the Fees Office
The Speaker represents the House of Commons' independence in dealing with the monarchy
Speakers are elected by MPs in a Commons vote, traditionally remaining in the role until retirement or death and re-elected automatically after general elections
Michael Martin was elected following the retirement of Betty Boothroyd in 2000
Veteran Conservative MP Sir Patrick Cormack likened the mood in the Commons to the mood in the nation for the Norway debate - said to be the moment Conservative MPs realised that Neville Chamberlain had to be replaced as prime minister.
And another Conservative MP, Richard Shepherd, said the public would not believe MPs were serious about reform as long as Mr Martin remained as Speaker.
Senior Labour MP Sir Stuart Bell stuck up for Mr Martin saying "the majority" of MPs would support his statement. He said there had "never been in the history of our land such an attack on the Speaker".
He added: "This House should calm itself down, should have a period of reflection and should support you as a Speaker is entitled to be supported."
The former Tory, now independent MP Bob Spink also spoke in favour of the Speaker, saying he did not want to see him "become a scapegoat for the action of these members".
Senior Lib Dem MP David Heath said the statement would have been welcomed a few weeks ago but he now had "very grave doubts" as to whether it would restore trust.
'Political death warrant'
Others sought advice on how a debate on the Speaker's future could be tabled.
Former shadow home secretary David Davis asked: "Is it within the power of a backbencher to put down a substantive motion and if so, how?"
There were shouts when Mr Martin said that was a matter for the government.
The leader of the main opposition party, a government in waiting, and his party cannot, I think act unilaterally to remove the Speaker in the House of Commons
Mr Martin also had to tell the Conservative MP Mark Field to watch his words when he suggested that some MPs had made fraudulent expenses claims.
Later Liberal Democrat MP Norman Baker, who was attacked by the Speaker last week for giving interviews about greater transparency on MPs' expenses, said Mr Martin "blew it".
"The effect of the statement is for the Speaker to have signed his own political death warrant ... I give him less than a week," he told BBC News.
The Speaker's critics blame him for various attempts to block requests in recent years to have expenses details released under Freedom of Information laws.
And he angered many by attacking MPs who had pressed for more transparency or criticised his decision to ask the police to investigate the leaking of expenses details to the Daily Telegraph.
Under parliamentary rules, the Speaker can either ignore the motion or ask for it to be debated in government time.
For MPs to openly criticise the Speaker breaks a long-standing Commons convention, while the last time a Speaker was forced from office was in 1695 - when Sir John Trevor was found guilty by the House of "a high crime and misdemeanour".
Mr Martin has been urged to stand down by Lib Dem leader Nick Clegg.
He told the BBC after the debate that it was now up to the government to decide whether Mr Martin's future was debated but added: "If the government won't do that I'm already looking at ways I can call that debate and the vote."
Prime Minister Gordon Brown declined to give Mr Martin his backing, saying that "the decision about who is Speaker is a matter for the House of Commons - it could never be a matter for the government".
The BBC understands Mr Brown spoke to the Speaker on Sunday about the situation.
Any move to unseat the Speaker would have to be supported by the Conservatives.
But Conservative leader David Cameron said the main opposition party could not "act unilaterally to remove the Speaker in the House of Commons - I don't think that would be right".
But a spokesman for Mr Cameron said later that the motion of no confidence in the Speaker should be debated, if it got enough signatures in order for his future to be resolved one way or another.
Mr Carswell confirmed earlier he had 15 signatures from "highly respected Parliamentarians from right across the political spectrum".
The BBC understands that number has now reached 18.
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