Tony Blair is preparing for the last big Commons rebellion of his premiership today as dozens of Labour MPs prepare to protest against his decision to replace Britain’s independent nuclear deterrent.

Mr Blair is almost certain to have to rely on the Conservatives to win approval to build a new fleet of nuclear submarines and to extend the life of their Trident D5 missiles.

There were signs last night that ministers had managed to cap the rebellion after a campaign by Gordon Brown, who came out in favour of keeping the strategic deterrent well before a formal decision was taken to replace it.

Allies of the Chancellor said that he had swayed at least seven Labour MPs, who had been ready to vote against the Government, to abstain or vote in favour and that he had “a long list of people to call”.

Rebels will be split between an amendment by Jon Trickett, a left-wing Labour MP, that urges a delay and that supporters claimed would be backed by up to 80 Labour MPs, and the option of voting against the government motion that seeks approval to replace Trident.

Labour sources said that the biggest revolt would probably be in support of the amendment, but a small group were withholding their support because it was tabled in alliance with the Liberal Democrats. Such MPs will break ranks in a second vote against the Government’s motion, although the size of this rebellion is expected to be smaller.

Signatories for the amendment include Sir Menzies Campbell, the Lib Dem leader. Compass, the left-wing pressure group chaired by Mr Trickett, announced that all 63 Lib Dem MPs would put their names to it.

Stephen Pound, the MP for Ealing North, became the third member of the Government to stand down yesterday when he resigned as ministerial aide to Hazel Blears, the chairman of the Labour Party, in order to vote against renewing Trident.

Jim Devine, MP for Living-ston, confirmed that he had given up his post as a ministerial aide. The Chancellor had attempted to talk him round and was also unsuccessful in trying to dissuade Nigel Griffiths, a long-time ally, from resigning from his unpaid post as Deputy Leader of the Commons. Mr Griffiths, whose seat of Edinburgh South has a majority of 405, will make a statement today.

It emerged yesterday that, despite claiming that the Cabinet decision to replace Trident had been subject to unprecedented debate, ministers rejected calls from within the National Executive Committee for wider debate within the party, a vote at its national policy forum and a free vote by Labour MPs. Six NEC members voted for such an extended consultation at a private meeting in January but were defeated, according to an account published by Ann Black, a Labour activist.

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