Sex scandal MP Nigel Griffiths set to stand down at election
Gordon Brown, left, with friend and ally Nigel Griffiths, who is standing down as an MP Picture: Rob McDougall
The news will come as a major blow to Prime Minister Gordon Brown, who counts Mr Griffiths as a key ally and a close personal friend.
Mr Brown would have been counting on his support in any bid to stay on as party leader if Labour loses the election.
However, it was thought doubtful that Mr Griffiths would be able to retain his seat following a sex scandal in 2008. The former minister allegedly had an intimate encounter with a brunette woman in his Westminster office.
Mr Griffiths, who has been married for 30 years, later apologised for engaging in sexual activity in his House of Commons office. He said he was ashamed of his actions, which he said fell below acceptable standards.
He was also criticised during the MPs' expenses scandal for claiming 3,605 for a plasma screen television.
In a letter to his local Labour Party, obtained by The Scotsman, Mr Griffiths said he had been offered the post of director of an international educational institution, with offices in London, the United States and India, starting in June.
The 54-year-old, who resigned as deputy leader of the House of Commons in 2007 over the government's decision to renew the Trident nuclear deterrent system, said: "I shall have lecturing responsibilities covering climate change, conflict resolution and nuclear disarmament, which, as you know, have been the focus of my constituency and parliamentary involvement for some time.
"I am delighted to have served the people of South Edinburgh over three decades.
"After 30 years of continuously elected service in Edinburgh, this is a once-in-a-lifetime opportunity and it would not be right to delay accepting this position, since I want to give the party time to select a new candidate to fight the forthcoming election."
During his 23-year career as an MP, Mr Griffiths carried out a variety of back-bench and ministerial roles. He was a whip in opposition between 1987 and 1989, and opposition spokesman for trade and industry between 1989 and 1997.
He rose to his most recent ministerial position in 2005 and held it for two years before leading a back-bench rebellion against the government over its plans to replace its existing nuclear weapons.
Earlier in his career, he was criticised for failing to declare that he owned a property that acted as his constituency office in Edinburgh's Minto Street.
In 2002, the Parliamentary Standards Commissioner found Mr Griffiths guilty of wrongly reclaiming 40,000 of rent for the office.
He used the money to boost a charitable trust fund that provided help for his disabled sister.
The Conservatives, who have already selected Dr Neil Hudson to contest Edinburgh South, will welcome an opportunity to take the lead in a seat it held for more than 20 years before Mr Griffiths was elected.
Dr Hudson said last night: "The voters know that this is a British general election, where there can only be one of two winners.
"We are gaining ground all the time. I'll leave Labour to sort out who their candidate is and get on with fighting to win the seat."
Mr Griffiths is the second key ally of the Prime Minister in three days to announce his resignation. The West Dunbartonshire Labour MP John McFall, currently chairman of the Treasury select committee, announced last Friday he would not be contesting the general election.
The 65-year-old said that, as he had reached a "normal retirement age", it was time for him to move on after 23 years as an MP.
Mr McFall was elected as the chairman of the Treasury select committee in 2001, before being re-elected to the position in 2005.
Friends of Mr Brown indicated at the weekend that he would be looking to remain in place as party leader if the Conservatives won the election with a majority of 20 seats or fewer.
A Labour spokesman said: "Nigel has served Edinburgh for more than 20 years and is one of the most experienced parliamentarians in Scotland, having been deputy leader of the House of Commons.
"He is known for his diligence in local matters and his fierce criticism of the current administration in the City of Edinburgh Council, which proposed to close 23 schools and nurseries, many in his constituency.
"Local members will now select a new candidate to fight the general election."
The spokesman added: "Our support in the seat remains strong and we will have campaign teams out knocking on doors in the coming days."
Before standing for parliament, Mr Griffiths was a member of Edinburgh District Council from 1980 to 1987.
In the 2005 general election, he held on to his seat by a narrow margin, with only 400 more votes that the Liberal Democrat candidate, Marilyne MacLaren, and about 4,000 votes ahead of the Conservative candidate, Gavin Brown.
In December, bookmakers predicted that Mr Griffiths would lose his seat at the general election if he ran again.
Both William Hill and Ladbrokes had at that time installed Dr Hudson as favourite to win the contest, with Ladbrokes giving him odds of 11/8. The Liberal Democrat candidate, former Edinburgh councillor Fred Mackintosh, was tipped to come second, at odds of 6/4, while Mr Griffiths, was in third place at 7/2.
NIGEL Griffiths was deputy leader of the House of Commons until 2007. Before that, he held a number of government positions, including minister for construction, minister for competition and consumer affairs, minister for coal health compensation, minister for small businesses, and minister for enterprise. He resigned from the government in March 2007 over his opposition to funding new Trident nuclear submarines.
The 54-year-old has also held a number of key positions in the community, including being a member of the Edinburgh International Festival Council, founder and chairman of Wester Hailes Citizens Advice Bureau, and a member of Wester Hailes Community School Council.
As an Edinburgh councillor during the 1980s, he chaired the council's housing committee. Mr Griffiths also formerly worked for a charity for people with learning difficulties.