FACTBOX-Britain's Speaker, the man and the role

May 18 (Reuters) - The British parliament's most senior figure, Speaker or presiding officer Michael Martin, apologised on Monday for an expenses scandal that he said had done terrible damage to the reputation of parliament.

Conservative legislator Douglas Carswell introduced a "no confidence" motion, backed by 15 legislators from the major parties, calling on Martin, 63, to step down.

It is the first direct challenge to the authority of a Speaker in more than 300 years.

Martin, speaker since 2000, sidestepped questions about his future and used parliamentary rules to postpone any debate on the no-confidence call [ID:nLI538520].

* WHAT HAPPENS NEXT?

-- Martin can resist attempts to oust him. As Speaker, he will decide whether he sets aside time for debate on the motion.

If he did step down, it could be seen as a blow to the prestige of Prime Minister Gordon Brown's Labour party, but the major parties might also hope it would satisfy public demands for tough action in response to the expenses scandal.

-- Martin, a former metalworker and union leader, was a veteran Labour politician when he became Speaker in 2000.

By tradition, the Speaker is a non-partisan figure and he cuts his ties with his political party once elected.

-- If Martin left immediately as Speaker, he would have to quit as a member of parliament, sparking a by-election in his Glasgow North East constituency, a prospect Brown would rather avoid at a time when Labour support has slumped due to the expenses scandal and the recession.

Following convention, the other major parties did not run candidates against Martin at the 2005 election.

A secret ballot would be held to choose the next Speaker, who would not necessarily be from Labour.

* WHAT DOES THE SPEAKER DO?

-- The Speaker chairs debate in the House of Commons, the lower chamber of parliament, keeping order and calling on MPs to speak.

-- The Speaker is the chief officer and highest authority of the House of Commons and must remain politically impartial. The Speaker is in charge of administration and represents the Commons to the monarch, the Lords and other authorities.

* MARTIN AND EXPENSES

-- Critics see Martin as "part of the problem" in the expenses controversy because he fought a long legal battle to prevent publication of the expense claims. They say a new Speaker is needed to oversee reform. Martin's supporters say he is being unfairly turned into a scapegoat for MPs' failings. -- Martin has been a controversial figure. In 2008, parliament's standards watchdog, John Lyon, investigated a complaint that his wife, Mary, had claimed 4,000 pounds on expenses for taxis. Lyon later dismissed the complaint, saying the taxi trips were reasonable.

-- Martin came under pressure after he and his assistants failed to uphold ancient parliamentary privileges and allowed police investigating government leaks to raid opposition Conservative politician Damian Green's office in November 2008.

* LIFE DETAILS:

-- Martin was born in Glasgow in July 1945 and became involved in the Sheet Metal Workers trade union and joined the Labour Party when he was 21. He worked as a shop steward at Rolls Royce in the early 1970s.

-- He became a Glasgow city councillor from 1973-1979 and was first elected as Labour MP for Glasgow Springburn in 1979.

* HISTORY OF THE POST

-- Nine Speakers died a violent death before 1560. There was one murder, one death during battle, and no fewer than seven beheadings - two on the same day.

-- If ousted, Martin would be the first Speaker to be sacked since Sir John Trevor lost his post for taking bribes in 1695. The position of a Speaker in British politics dates back to the 13th century.

Sources Reuters/House of Commons/BBC/UKPollingreport/TheyWorkForYou.com (Writing by David Cutler and Adrian Croft, London Editorial Reference Unit)