Chancellor Gordon Brown was yesterday hit by a left-wing backlash after saying he wanted to secure "for the long term" Britain's independent nuclear deterrent.
Former Cabinet Minister Clare Short and other left-wing MPs denounced his determination apparently to replace the UK's ageing Trident weapon system.
Ms Short said she could no longer support Mr Brown as a successor to Prime Minister Tony Blair.
Earlier, Downing Street promised a White Paper spelling out the Government's intentions, followed by a "proper debate" on the issue.
Speaking at the Lord Mayor's annual banquet in the Mansion House, the Chancellor said that the Government would show "strength of national purpose" in "protecting our security in this Parliament and the long-term - strong in defence in fighting terrorism, upholding Nato, supporting our Armed Forces at home and abroad, and retaining our independent nuclear deterrent."
Ms Short attacked Mr Brown, saying: "To do it in a speech without consultation is both the wrong decision and is disrespectful of any kind of democratic process."
She added: "It means a lot of people who were happy to see Brown take over as leader will now think there's got to be a contest and we're not willing to support him."
Ms Short said it was part of a "desperation" by Mr Brown to win the backing of Blairites as the next leader.
Asked if she believed Mr Brown's chances of succeeding to the leadership had been damaged, she said: "People are feeling more and more disillusioned and more and more people feeling Gordon won't put anything right and will just continue with all the errors that are being made."