Mr Purnell says the question of Mr Brown's leadership needs to be put
One of the fastest-rising stars in the Labour Party, Work and Pensions Secretary James Purnell has risked his career by becoming the first cabinet minister to tell Gordon Brown directly that he should quit.
In his resignation letter to the prime minister, Mr Purnell wrote: "I owe it to our party to say what I believe, no matter how hard that will be.
"I now believe that your continued leadership makes a Conservative victory more, not less, likely. That would be disastrous for our country."
It was Gordon Brown who handed Mr Purnell one of the biggest jobs in government at the age of 37.
In January 2008, Mr Purnell took control of the largest budget in Whitehall as work and pensions secretary when he replaced Peter Hain.
The loss of a young minister in a crucial reforming role, who had been tipped for even greater office, will be a huge blow to the prime minister.
Mr Purnell is known to be close to one of the possible front-runners for the leadership, Foreign Secretary David Miliband. However in his resignation letter, Mr Purnell denied he was acting with anyone else.
He also said he was not seeking the leadership himself.
In recent weeks Mr Purnell has been one of the Labour MPs forced to defend his expenses claims.
The Daily Telegraph alleged that he avoided paying capital gains tax on the sale of a London flat after claiming expenses for tax advice from an accountant.
Mr Purnell (right) was superimposed on a picture of a hospital photocall
A spokesman said any suggestion that he avoided capital gains tax was "completely untrue".
He has also faced two security embarrassments in recent months. He had to apologise after leaving confidential ministerial correspondence on a train in November.
Two months later it emerged that he lost his wallet, containing a Parliamentary security pass, on a busy central London street.
Before he resigned from cabinet, Mr Purnell was in the process of steering his controversial welfare reform bill through Parliament. The bill represents the government's latest attempt at getting more people off benefits and into work.
It includes benefit sanctions for people who miss Jobcentre appointments and a requirement that people on employment and support allowance undertake 'work-related activity'.
Mr Purnell is one of a close-knit group of young ministers promoted into the cabinet by Gordon Brown. His former flatmate Andy Burnham, took over his old job as culture secretary when he moved to the work and pensions brief.
As culture secretary, his first big statement to MPs was to confirm Mr Brown's decision to halt plans for a super-casino - a U-turn Downing Street insisted was made in consultation with Mr Purnell.
He also warned the TV industry to "get their house in order" after a series of "fake" scandals.
But shortly afterwards, he found himself embroiled in a fakery row of his own after it emerged his image had been electronically inserted into a group photograph of dignitaries celebrating a hospital project.
His department admitted later it had received an e-mail telling it about the superimposed image before it was sent to the press but that the message had not been shown to the secretary of state. Mr Purnell denied all knowledge.
The son of an accountant and a teacher, Mr Purnell was born in Guildford, Surrey, and partly educated in France, at the prestigious Lycee International School, at St Gerrain en Laye.
He studied philosophy, politics and economics at Balliol College, Oxford, while working as a researcher for the future prime minister, Tony Blair.
His first job was as a consultant at Hydra Associates, followed by a research fellow position at the Institute for Public Policy Research think-tank.
He went to work for the then BBC director general - and later Downing Street adviser - John Birt, rising to be head of corporate planning.
This was followed by four years as Tony Blair's special adviser on the media.
A former Islington councillor, he became one of Labour's youngest MPs at 2001 general election when, at the age of 31, he won the safe seat of Stalybridge and Hyde.
He served his apprenticeship in the Treasury, as an aide to minister Ruth Kelly, at the Cabinet Office and as a junior whip.
His first high-profile ministerial position was at the Department for Culture, Media and Sport, where he steered controversial round-the-clock drinking laws through Parliament as well as modernising tax breaks for the film industry.
In 2006, he switched to the pension reform brief, where his energy and commitment won plaudits from industry.
He was named Which? Consumer Champion of the Year for developing the national pensions saving scheme.
A keen footballer and Arsenal fan, he played in the same team as Mr Burnham: Red Menace and its successor Demon Eyes.
He also lists cinema, theatre and golf among his leisure interests - he was among backbench MPs who lobbied the EU over the Premiership's TV deal.