An expense claims scandal is plaguing the Speaker of Britain's House of Commons, Michael Martin, shown in December 2008 during the state opening of Parliament at the Palace of Westminster in London. (Matt Dunham/Associated Press)

The Speaker of Britain's House of Commons announced his resignation Tuesday over his handling of the expense claims scandal, becoming the first person in 300 years to quit the post.

Michael Martin told MPs in a packed sitting of the House that he would step down on June 21 in order to maintain unity.

"In order that unity can be maintained, I have decided that I will relinquish office of Speaker on Sunday 21 June," he said in a short statement.

"This will allow the House to proceed to elect a new Speaker on Monday 22 June."

Martin, a member of Brown's governing Labour party, has been criticized for his handling of the scandal, which saw public officials claim tax money for inappropriate expenses such as constructing swimming pools, paying off mortgages and buying luxury furniture.

Critics allege he ignored warnings the expense system needed reforms and tried to block publication of the claims.

In an attempt to suppress calls for his resignation on Monday, Martin apologized and pledged to lead efforts to restore Parliament to respectability.

"Please allow me to say to the men and women of the U.K. that we have let you down very badly indeed," Martin told legislators in the Commons. "We must all accept the blame and to the extent that I have contributed to the situation, I am profoundly sorry."

As Speaker, Martin chairs debate in the House of Commons and calls on MPs to speak. The role is expected to be non-partisan.

Britain's main opposition leader, David Cameron, said he will ask members of the public to sign a petition urging Brown to call an election as soon as possible, offering voters a chance to kick out lawmakers who have abused expenses.

While Cameron has been agitating for an election for months, his reasoning appears to have changed — and may strike a chord among a British public outraged over the daily revelations of tax money used for constructing swimming pools or other inappropriate expenses.

The final decision on an election rests with Brown, who must call one by mid-2010 and is expected to wait until the last possible moment, hoping for the economy to revive.

Opposition polls suggest Brown's Labour party is lagging behind Cameron's Conservatives.

Martin is the first Speaker to be forced out since John Trevor was deposed in 1695 for accepting a bribe.

With files from The Associated Press