THE final say over whether Britain replaces its Trident nuclear deterrent will rest with MPs, Jack Straw, Leader of the Commons, said yesterday.

Until now, Tony Blair and his ministers have avoided conceding a vote, saying only that there would be a "full debate".

However, yesterday during Business Questions in the Commons, Mr Straw surprised MPs by saying there would be a "substantive vote" on the issue. The government hopes, with Tory backing, to win it.

"We would anticipate that the majority of members would support this. There will be a vote and everybody understands the consequences of it, " said Mr Straw.

Although the life of the Trident missile system runs until 2024, the Prime Minister has made clear a decision on replacing it will be made this year. The four submarines are based at Faslane on the Clyde.

Gordon Brown, the Chancellor and Mr Blair's expected successor as Prime Minister, backs replacing Trident, at a cost estimated at up to GBP25bn.

Mr Straw made clear he thought the majority of Labour MPs, as well as Conservatives, would support the move to replace Trident.

Mr Straw's announcement was welcomed by the Campaign for Nuclear Disarmament but it called for a full public debate on the issue before MPs voted.

Last night, Pete Wishart, for the SNP, also welcomed the government's move, describing it as a "major concession".