HOUSE of Commons Speaker Michael Martin announced that he intends to stand down on June 21, so becoming the first Commons Speaker to be effectively forced out of office for 300 years.

The Glasgow North East MP has been an MP for 30 years and Speaker for nine.

In his statement, Speaker Martin said: ‘I have always felt that the House is at its best when it is united. In order that unity can be maintained, I have decided that I will relinquish office of Speaker on Sunday, 21 June.

‘This will allow the House to proceed to elect a new Speaker on Monday, 22 June,’ and he finished by adding ‘that is all I have to say on this matter.’

Martin’s spokeswoman said he would also stand down as MP for Glasgow North East on June 21, sparking a by-election in what has been considered a safe Labour seat.

Martin’s critics say he was the driving force behind repeated attempts by House of Commons authorities to block details of MPs’ expenses from coming out under the Freedom of Information legislation.

But his supporters say he has long been the victim of snobbery and has been made a scapegoat for the expenses scandal.

Meanwhile, the Metropolitan Police have said they will not investigate how details of MPs’ expenses claims came to be leaked to the Daily Telegraph.

A Met spokesman claimed that the ‘public interest defence would be likely to prove a significant hurdle’ to a criminal prosecution.

The decision not to investigate the leak was taken at a meeting between the CPS and officers from the Met’s Economic and Specialist Crime Command, a Scotland Yard spokesman said.

But Met Commissioner Sir Paul Stephenson made clear that some MPs may not get off so lightly, announcing that officers from the Economic and Specialist Crime Command had met senior Crown Prosecution Service solicitors to discuss allegations that some MPs had misused public money.

Gordon Brown said yesterday that no Labour MP who had broken expenses rules would be allowed to stand at the next election.

Brown said MPs were elected to serve the public rather than themselves and insisted he was committed to a ‘complete clean-up of the system’.

Former Conservative minister Douglas Hogg said he would stand down as an MP at the next general election.

Hogg has already agreed to repay £2,200 – the cost of clearing a moat at his country estate – which had been on paperwork submitted to the Commons fees office in support of his claims.