THE SNP is set to defy Westminster convention by standing in the General Election against the Speaker of the House of Commons, Mr Michael Martin.

Mr Martin - elected on Monday to succeed Ms Betty Boothroyd - represents the Glasgow constituency of Springburn, where he held the seat easily for Labour in Tony Blair's 1997 landslide.

When Ms Boothroyd stood last time in West Bromwich West, she was unopposed by the Tories and Liberal Democrats, and had to face only to fringe candidates.

She and previous Speakers have enjoyed virtual immunity from challenges from rival parties because they stood as Speaker and not for any political party. Mr Martin is expected to do the same.

But the SNP confirmed last night it would be putting up a candidate in Springburn. ''Having the chance to vote for Scottish independence is much more important that the conventions of the Westminster Parliament,'' said a Nationalist spokesman.

He added: ''But we congratulate Mr Martin on his success. It is a great achievement to attain such distinguished office, especially for a man from his working class background, and the fact that he is the first Roman Catholic holder of that office since the Reformation.''

Mr Martin is not exactly in immediate peril of losing his seat. He cruised home in the General Election with more than 71% of the vote and a majority of 17,326. The SNP came second with only 16.5%.

SNP policy, confirmed by its annual conferences, is to contest every seat in Scotland on the independence ticket. ''What matters most to the Scottish people is democratic choice,'' said the SNP spokesman. ''We don't feel bound by Westminster convention.''

The SNP candidate will be 52-year-old Sandy Bain, a retired principal teacher of geography. He is a Glaswegian SNP activist and is married with a daughter.

Meanwhile, pressure was mounting last night on the Commons Procedure Committee to scrap the current arcane process of electing a Speaker and introduce a modern ballot system should there be the expected General Election next spring and another contest run at the start of the new Parliament.

Liberal Democrat Chief Whip Paul Tyler, calling for a review, said: ''Even at the final vote to confirm the new Speaker, the number of votes fell far short of the total number of MPs.''