The Speaker of the House of Commons was in danger of becoming the biggest victim of a row over British lawmakers' expenses as the leader of one of the main parties joined calls yesterday for him to resign.

Michael Martin, the top authority in the lower parliamentary chamber, has been accused of being an obstacle to reform of the expenses system, whose failures have been highlighted in embarrassing detail in recent days.

Amid public outrage about claims for everything from moat-cleaning to luxury televisions, the leader of the second opposition Liberal Democrats, Nick Clegg, said Mr Martin had to give way to a new speaker who could drive through change.

"I have arrived at the conclusion that the speaker must go," Mr Clegg told BBC television.

"He has proved himself over some time now to be a dogged defender of the way things are, the status quo, when what we need, very urgently, is someone at the heart of Westminster who will lead a wholesale radical process of reform."

Britain's Sunday Times newspaper, quoting a former Martin aide, reported allegations the Speaker had presided over a so-called "reign of terror" as he blunted bids to reform the system.

Today, an MP from the main opposition Conservatives is due to table a motion of no-confidence against the Speaker. Douglas Carswell said he had "significant" support from lawmakers of all three main parties.

Mr Martin was a long-time member of Prime Minister Gordon Brown's Labour party, but renounced his political loyalties when he took office as Speaker in 2000. He is expected to make a statement to the House of Commons today.

His spokesman would not be drawn on the resignation row, saying only that his remarks would be "focused on how to resolve the problem of allowances as swiftly as possible".

Elected by lawmakers and the highest authority in the House of Commons, the speaker traditionally stays in the job until he retires. The last time a post-holder was forced out was more than 300 years ago.

However, a peer from the Labour party, Lord Foulkes, blamed "bitter former ministers" for the campaign against Mr Martin and said he did not expect the Speaker to bow to the pressure.