Ministers were last night bracing themselves for a major Labour backbench revolt in this week's crucial Commons vote on the replacement of Britain's Trident strategic nuclear deterrent.
Claims that up to 100 Labour MPs could vote against the Government or abstain in the division on Wednesday were underlined by a poll suggesting that almost two thirds opposed Trident renewal.
Of the 101 Labour backbenchers who responded to a survey by BBC Radio 4's The World This Weekend, 64 said they were against Trident renewal.
Only 22 backed the Government's plan to acquire a new generation of nuclear missile submarines and to update the Trident D5 missiles, while 15 said they were still undecided.
A revolt of that scale would force the Government to rely on the support of the Tories to carry the vote.
Already one ministerial aide - Jim Devine, the parliamentary private secretary to Health Minister Rosie Winterton - is reported to be ready to quit and it is thought that others could follow.
Defence Secretary Des Browne said that he did not believe the revolt would be as big as some of the rebels were predicting.
However, Labour backbencher Jon Trickett, who is tabling an amendment calling for a decision on renewal to be delayed, said that he had the support of "well over 60" Labour MPs.