Is Mr Speaker the victim of a classist campaign in the Commons?

He's a "drongo", a "duffer", a man with "mental, moral and emotional difficulties" who comes "from the same chimp farm as Two Jags". And that's just what they say in public.

But this torrent of personal abuse has not been directed at a particularly slow Premiership footballer or a lifer just freed from Broadmoor. It has been showered on Michael Martin, the 156th Speaker of the House of Commons and one of the most senior figures in Britain's unwritten constitution.

Yesterday, news emerged that Mr Martin, 57, MP for Glasgow Springburn, had been so upset by recent criticism that he had told friends he was the victim of Westminster "snobbery" and "anti-Scottish" prejudice. The former sheet metal worker also took the unprecedented decision to authorise a statement announcing his intention to stay on after the next general election. The reason for this was ostensibly a newspaper report at the weekend claiming that Charles Clarke, the Labour Party chairman, had said the Speaker was "an embarrassment" and had "lost credibility".

Mr Clarke strongly denied the story, saying the quotes attributed to him were "entirely invented". He added that he was not one of a reported group of ministers who claimed Mr Martin was a liability and he did not hope he would be shuffled off to the Lords.

Nevertheless, the latest claims echo concerns voiced by some ministers and backbenchers since October 2000, when Mr Martin succeeded Betty Boothroyd to the post. Some ministers had preferred the former Tory minister Sir George Young, in line with the convention of replacing a Labour Speaker with someone from a different party.

However, his enemies had badly underestimated not just Mr Martin's store of goodwill on the back benches, but also his supporters' ability to arm-twist, cajole and enthuse MPs for vote for him. Despite the threat of 11 rival candidates, he was elected by a huge majority.

Even so, his career has been dogged by the perception that he is not right for the job and claims that he errs on matters of procedure and fairness.

He infuriated Tories by ordering John Butterfill MP – who had questioned the order of speakers in an Arab-Israeli debate – to leave the Chamber. He ignored convention, and was forced to apologise, when he praised the Government's asylum policy. Most controversially of all, he intervened last week at Prime Minister's questions to order Iain Duncan Smith not to ask Tony Blair about his role as leader of the Labour Party. To make matters worse, he then told Mr Blair not to refer to Tory policies either.

Mr Martin's critics pounced on the incident, saying it was an example of his unfitness for the office of Speaker. But although the Parliamentary sketch writers had a feeding frenzy, no MP was willing to go on the record to attack Mr Martin.

Some MPs think his defence of "snobbery" is a cover for his inadequacies. But his allies believe that he is genuinely a victim of the class war at Westminster. "They attack his accent, his background, everything. He has been elected fairly and should be left alone," said one.

Peter Bradley, Labour MP for The Wrekin and not one of Mr Martin's original supporters, said: "He's not treated the job as showbusiness, unlike Betty, and perhaps that's because he hasn't got as big an ego as some. I've got no problem with the way he has done his job."

Certainly, one of Mr Martin's biggest problems has been Baroness Boothroyd's indirect but constant commentary. Only last week, she told friends at a lunch: "I can't get over how many people still address me as Madam Speaker, you know." One Martin ally retorted yesterday: "It's like John Major being dogged by Maggie Thatcher. She won't let go."

Tam Dalyell, the Father of the House, gave Mr Martin his strong backing yesterday, saying the real problem with Prime Minister's questions was "toadying" and "vomit-making" questions from backbench Labour MPs.

For several centuries, the Speakership was a precarious post to hold, with no fewer than nine killed in the Middle Ages and the Tudor period. Five were beheaded at the behest of the King, one died in the Tower, one fell in battle, one was murdered by rivals and one was beheaded by a mob while trying to escape, disguised as a monk.

Today, the only real reminder of how risky the office once was is the tradition of a new Speaker being "dragged to the Chair" by his supporters as he puts up a show of resistance. Whatever his opponents may do, though, Mr Martin intends his own resistance to recent criticism to be more than token.