EDINBURGH MP Nigel Griffiths today quit his government job to lead a backbench rebellion against the replacement of the Trident nuclear deterrent.
The Deputy Leader of the Commons gave up his post to join other Lothian MPs planning to vote on Wednesday against the renewal of the submarine based weapons system.
His move came despite heavy pressure from fellow ministers and his political patron Gordon Brown to change his mind and back the Government, after telling his constituency party he would object to any move to spend billions of pounds on a new nuclear deterrent.
Mr Griffiths told the Evening News: "I have resigned from the Government. I found I could not support the replacement of the Trident nuclear deterrent.
"I shall be leaving my job as Deputy Leader of the Commons and the government with a heavy heart and a clear conscience.
"I intend to make a personal statement to the Commons in the next few days as I want other MPs to hear my reasons first."
Mr Griffiths sent a letter to the Prime Minister tendering his resignation.
One senior ministerial source commenting on the Edinburgh South MP's decision said: "MPs have surprisingly strong views on this issue."
On suggestions that the scale of the rebellion could reach 140 MPs - leaving Prime Minister Tony Blair and Mr Brown relying on Tories to get the measure through the House of Commons - the source said: "I just don't know. It's going to be big.
"The time is wrong with Tony Blair's authority waning. I would suspect it will be closer to 60 once all the normal processes have been gone through."
And other sources confirmed that Mr Griffiths had been under heavy pressure from Mr Brown to change his mind and toe the line.
At least 12 Scottish Labour MPs are understood to be ready to vote against the Trident replacement, including Midlothian's David Hamilton, Linlithgow and East Falkirk's Michael Connarty, Edinburgh East's Gavin Strang and Livingston's Jim Devine who has already quit as Parliamentary Private Secretary for Health Minister Rosie Winterton in readiness to vote against Trident.
But Edinburgh South West MP and Trade and Industry Secretary Alistair Darling, along with East Lothian's Anne Moffat, will be voting with the Government.
Mr Darling said: "I have changed my mind over the last 25 years. I shall be voting to replace Trident because I think nuclear weapons are now proliferating. If I believed that not replacing it would help multilateral disarmament, I might vote differently. But I don't."
Mrs Moffat said: "I shall be supporting the replacement of Trident because I think in the current uncertain world there is a need for it."
Mr Lazarowicz said: "I cannot back spending such large sums of money for a weapons system the need for which is at the least questionable."
And Mr Connarty praised Mr Griffiths for putting his principles above his job, saying: "There is the moral argument and I can't see a British government using such a weapon. It will also mean we are once again following questionable American foreign policy which seems to be aimed at subduing the world.
"If we are going to spend up to 80 billion on new weapons, we should spend them on conventional defences.
"I must praise Nigel for his decision to resign. Not many people put principles above their government job."
But at least one Labour MP - John Mann - rejected claims he was to quit his job as a PPS and vote against the government blaming a CND "dirty tricks campaign".
Nigel Griffiths was born in Glasgow in 1955 but moved to the Capital after studying at Edinburgh University - where he was first introduced to the then rector Gordon Brown.
Following his studies, he worked as a secretary to the Lothian Development Council, before becoming a welfare rights worker.
He was elected as an Edinburgh councillor in 1980 and, during his tenure, worked with Anita Roddick to found the Big Issue in Scotland. He held the council position until being elected to parliament in 1987, when he ousted the sitting Conservative MP Michael Ancram by 1859 votes. He was made an Opposition Whip by Neil Kinnock in 1987, becoming a spokesman for eight years on trade and industry in 1989.
He became Parliamentary Under Secretary of State at the Department for Trade and Industry in Tony Blair's first government in 1997, but lost the post in the Prime Minister's first reshuffle the following year.
He later returned to the same position following the 2001 election and, from 2005 until today, has served as deputy to the Leader of the House of Commons, Jack Straw.