Support for the Commons Speaker Michael Martin was waning last night as he faced an unprecedented wave of criticism for his handling of the Damian Green affair.
Senior MPs expressed profound concerns about Mr Martin's position as some warned that backbenchers would move to block his reappointment if he attempted to carry on beyond the next election.
Mr Martin will today chair an emergency three-hour debate on the arrest of Mr Green, the Conservative immigration spokesman whose Commons office was raided by officers investigating a string of leaks from the Home Office.
Yesterday Mr Martin's spokeswoman indicated he would be prepared to carry on as Speaker after the next election, but stressed he would listen to the concerns of his constituencies in the House of Commons and his Glasgow parliamentary seat. Critics reacted with alarm, as a survey of backbenchers carried out by the BBC found 32 of the 90 MPs who took part said they had lost confidence in Mr Martin, with 50 believing he was "culpable". Some MPs warned that backbench critics of the Speaker would try to vote down his reappointment if he tried to retain his job after the next election.
The raid on Mr Green's Commons office has provoked fury in all parties at Westminster and led a series of MPs to take the unheard-of step of openly criticising the Speaker and even calling for him to step down.
Yesterday even David Cameron, the Conservative leader, made plain his concern, stopping short of saying he had confidence in Mr Martin, saying instead: "I want to have confidence in the Speaker and the Speaker's office. Things need to be done to put right the situation."
MPs stressed that any attempt to sack Mr Martin before the next election was highly unlikely, but pressure was growing for him to stand down. Under rules adopted in 2001, the Commons must formally appoint the Speaker at the start of each Parliament. Normally a sitting speaker would be re-elected by acclamation, but procedures exist for a speaker's reappointment to be voted down in extremis.
Bob Marshall-Andrews, the Labour left-winger who last week called for Mr Martin to resign over the affair, said the Speaker would face a challenge if he tried to carry on after the next election. He said: "I think people will stand against him. I think it would be very sad if he did [stand again]. There is not a chance he would be re-elected. It would be a very sad way for him to go. He ought to go in a dignified way."
The former deputy speaker Michael Morris, now Lord Naseby, told the BBC Mr Martin had "let the House of Commons down". He said: "Why the Speaker was not in the lead role is something I find absolutely incomprehensible. He needs to reflect on that situation. I don't think that it is for the members to necessarily put down a motion of no confidence, because that is a very drastic stage, but I think he needs to reflect on his position frankly."
Mr Martin will face criticism today over plans to set up a panel of seven senior MPs to investigate the raids on Mr Green's parliamentary office. Liberal Democrats have already pledged to boycott the investigation, saying it will be Labour-dominated and will not sit until police inquiries have finished.
Sir Malcolm Rifkind, the former Conservative foreign secretary, told the BBC there was widespread concern about Mr Martin's handling of the affair. He said: "I think most members of Parliament, regardless of political party, believe the way in which these matters were handled in the last week was seriously flawed."