Prime Minister Tony Blair's troubles over Trident deepened last night after the Deputy Commons Leader Nigel Griffiths quit in protest at the Government's decision to renew Britain's nuclear deterrent.
Mr Griffiths resigned from his unpaid post, saying he did so "with a heavy heart but a clear conscience" - and may be followed by more junior ministerial aides.
But Tory leader David Cameron renewed his pledge to side with No 10 over the decision to update the UK's submarine-based nuclear arsenal, ensuring parliamentary success for Mr Blair tomorrow night.
Two further ministerial aides, Jim Devine, Parliamentary Private Secretary to Health Minister Rosie Winterton and Stephen Pound, PPS to Labour chairwoman Hazel Blears, have said they are considering their position on the lowest rung of the Government ladder.
Mr Pound confirmed he would "certainly" not be voting for replacing the existing missile system but was waiting to talk to Government whips before considering resigning his position.
Mr Griffiths said: "I am resigning with a heavy heart but a clear conscience.
"I intend to make a personal statement in the House of Commons to colleagues and it is only right that they hear the reasons first."
He also said he had sent a so-far unpublished letter to the Prime Minister tendering his resignation.