Michael Martin will this afternoon announce his plan to resign as Commons Speaker, it was revealed today.

The news came as an unprecedented motion appeared on the House of Commons order paper, signed by 23 MPs, calling for Martin to resign because of his failure of leadership over the expenses scandal.

Martin will make a statement to MPs at 2.30pm announcing his resignation, according to Whitehall sources. It it thought that he will not step down with immediate effect, but will tell MPs that he will resign soon, possibly before the summer recess.

It was not immediately clear whether he would also resign his seat, triggering a byelection in his Glasgow North East constituency. By convention, retiring Speakers are offered a peerage and it is widely expected that Martin will take a seat in the House of Lords.

The Speaker will be the most high-profile casualty of the expenses catastrophe. Some MPs believe that he has been made a scapegoat for the failure of the Commons as a whole, although Martin has faced persistent accusations of incompetence since his election in 2000.

Under new Commons rules already agreed, the next Speaker will be chosen by secret ballot.

Today one bookmaker made Sir George Young, the Tory former transport secretary, the favourite to succeed Martin.

Sir Alan Haselhurst, the Tory MP who is the most senior of the three deputy Speakers, and Sir Menzies Campbell, the former Liberal Democrat leader, are also strong contenders for the post.

Martin appeared to have lost the support of all three main party leaders. Nick Clegg, the Liberal Democrat leader, has openly called for his resignation, David Cameron, the Tory leader, signalled today that he wanted the no-confidence motion to be called, and Gordon Brown, the prime minister, has now given up saying that he thought Martin was doing a good job.

Downing Street would not comment on reports that Brown met Martin this morning to discuss his future. Downing Street announced that Brown will give one of his regular press conferences later today, at 5.30pm.

But what seems to have persuaded Martin to go was the reaction when he made a statement in the Commons yesterday apologising for his role in the expenses affair. In scenes for which there is no precedent in modern times, MPs from all sides of the house told him to his face that he ought to go.

Martin, a former sheet-metal worker from Glasgow and the first Catholic in history to hold the office of Commons Speaker, was seen as an obstacle to reform because he chairs the House of Commons commission, the body in charge of Commons administration.

When campaigners tried to obtain information about MPs' expenses under freedom of information legislation, the commission fought the case at every stage – even going to the high court at considerable legal expense when many lawyers said the case was hopeless.

Eventually the commission lost, and it agreed to prepare details of MPs' expenses for publication this year. But Martin came in for further criticism when the Daily Telegraph started publishing leaked details about the claims because, instead of accepting that publication was legitimate, the immediate reaction of the Commons authorities was to call in the police to ask them to investigate.

On Monday last week Martin also astonished some MPs when he criticised two MPs in the chamber, Labour's Kate Hoey and the Lib Dem Norman Baker, because they had been critical of the House of Commons commission's handling of the issue.

Yesterday in the Commons, a raft of MPs stood up and publicly called for him to go in one of the most extraordinary parliamentary episodes of modern times.

Alistair Graham, the former chairman of the committee on standards in public life, said that Martin was an obstacle to reform.

"He did rather act like a shop steward for MPs and he didn't have the stature and charisma once the crisis hit parliament to find a way through so he was just the wrong person for that situation and hopefully parliament is now going to put that right," Graham said.

Today Baker said that Martin's decision was "the right decision to take". He said that although Martin had had "immense difficulties", he had also made some positive contributions that should be remembered.

"He had to go for the sake of parliament. That does not stop us feeling sorry for him on a personal basis," Baker said.

Carswell said it gave him no pleasure to have played a part in bringing Martin down, but said the House of Commons needed a new Speaker to help guide it out of the current crisis.

The Harwich and Clacton MP told Sky News: "I have acted not as his enemy and least of all as an opposition MP. I have acted as somebody who cares passionately for the parliamentary system.

"I believe we have found ourselves in a moral ditch and we need reform and change to get out of that ditch and restore dignity to politics.

"It gives me no pleasure to have done this at all, but it was necessary to do it. We need a new Speaker who understands that 'sovereignty of parliament' is shorthand for 'sovereignty of the people'.

"The reason why I think we need Michael Martin to step down is because he not only presided over this system, he actively sought to prevent reform."

Paul Flynn, a Labour MP who signed Carswell's motion of no-confidence, said: "I'm afraid that [Martin] has brought this on him self. Parliament has to reform itself. He was the wrong person to do it."

Flynn said that some of the attacks on Martin were unfair, but that it was wrong for Martin to attack the "whistleblowers" who had complained about the Speaker's handling of events.

Flynn also said that he would be supporting the Tory MP John Bercow as the next Speaker because he had the potential to produce "radical reform".

Tony Wright, the Labour chairman of the public administration committee, said there was a "groundswell of opinion" that made Martin's position untenable.