In an interview with the Financial Times, Jon Cruddas, the Labour MP for Dagenham and one of several contenders in the race to replace John Prescott as the party's deputy leader, said a rebel amendment calling for a longer debate was likely to be tabled ahead of a crunch Commons vote expected on March 14.
Mr Cruddas said ministers had failed to allow suf-ficient time for a debate on Trident's replacement and that a promised con-sultation within the Labour party had not yet happened. MPs will have one day to debate and vote.
While insisting he was not against having a nuclear deterrent in principle, Mr Cruddas said there were serious questions over whether such weapons were an appropriate use of taxpayers' money in a post-cold war world.
"I haven't been convinced," he said. "I've never been a member of CND, I come from a military family for God's sake. My old man was in the navy for 27 years, he actually worked with this sort of weaponry, so it's not out of a base camp of hostility, a unilateralist base camp.
"But it seems to me pretty self-evident we should have quite a mature discussion about whether this is the contemporary weaponry to deal with the contemporary threat or whether this is a hangover from a previous epoch."
A Commons motion calling on the government to extend an "insufficient" consultation period of three months has been signed by 142 MPs from seven political parties, including 78 Labour backbenchers.
Mr Blair may be forced to rely on Conservative support to win the Commons vote.
Jon Trickett, the Labour MP who tabled the motion, said: "It feels as if we're being made to make a decision rapidly, under whips' pressure, and on the basis of inadequate information.
Mr Blair has said new nuclear-armed submarines would cost between £15bn and £20bn over 30 years and take up 3 per cent of the entire defence budget each year.
"Is this the most effective prioritisation of resources? It's an awful large sum of money," said Mr Cruddas.
Des Browne, the defence secretary, is preparing to address the parliamentary Labour party on Monday, where he will be able to gauge the scale of any dissent.
Aides said he had been speaking to MPs about their concerns over the past few months.
Mr Cruddas conceded he was "the outsider" in the deputy leadership contest but was confident of getting on the ballot paper. If elected, he would be a "transmission belt" between the party and government, acting as a voice for ordinary members in cabinet.