Mirror journalist Paul Routledge's book on the former trade secretary, although not even published at the time, is widely credited with Mr Mandelson's fall from office on 23 December 1998.

Mr Mandelson was forced to leave the government after The Guardian printed details of a secret loan between Mr Mandelson and the Paymaster General Geoffrey Robinson.

The story was to form one of the centre pieces of Mr Routledge's book - he claimed to have had the story for over a year - although how the story leaked to The Guardian remains a mystery.

With the resignation of Mr Mandelson the government lost the one man after Tony Blair most responsible for the creation of New Labour, the election winning political formula that brought the Labour Party back to power after 18 years in the wilderness.

But Labour backbenchers are far from keen on having the master strategist return to government anytime soon, saying he most remain one of them for a year or two at least to atone for his error of judgement.

Always a controversial figure, Mr Mandelson was one of the main driving forces behind the modernisation of the Labour Party even before Mr Blair became party leader after the death of John Smith in 1994.

With his resignation from the government the prime minister sees one of his closest friends and key allies leave the Cabinet table.

Architect of New Labour's image

Mr Mandelson was the second member of the Cabinet to resign after former Welsh secretary Ron Davies resigned in October after a "moment of madness" on Clapham Common.

Mr Mandelson only took up his job at the Department of Trade and Industry in July's re-shuffle. Previously, he had spent over a year as Minister Without Portfolio, a trouble shooting role which enabled him to use his mastery of the arts of spin to present government policy in the best light.

Despite being acknowledged as a presentational genius, Mr Mandelson was never widely liked inside the party. Those on the left, often treated him with suspicion because they saw him as being partly responsible for the leadership's decision to ditch many of Labour's traditional socialist principles.

As well as being trade secretary he was as the minister in charge of the much-criticised Millennium Dome in Greenwich.

His political star first started to rise when he became Labour director of communications from 1985 to 1990 under the then Labour leader Neil Kinnock.

His ability to identify the message needed to win back public support was invaluable to the revival of the party after its years in opposition.

Mr Mandelson was born into a Labour family - his grandfather was a Labour Cabinet minister Herbert Morrison - but he rebelled and joined the Young Communist League after Labour supported the United States' intervention in Vietnam.

It was during this period that he attracted the well-documented attention of the MI5 intelligence service.

Peter Mandelson entered Parliament in 1992

His rapid return from the far left began when he won a place at St Catherine's College, Oxford. Prior to this, he spent a year working in Tanzania under the aegis of Archbishop Trevor Huddleston, the anti-apartheid campaigner.

He started on the road to party politics through a job at the economics department of the Trades Union Congress and from there joined Lambeth council, from 1979 to 1982, during its "loony left" days.

Mr Mandelson moved on to become a producer for London Weekend Television, from 1982 to 1985, working on political commentator Brian Walden's programme. It was here that he befriended BBC Director General Sir John Birt.

He left to take up the role of Labour's director of communications, but his real ambition was a place in Parliament. He resigned in 1990 to contest the Hartlepool seat, which he won in 1992.

Derek Draper: Embarrassed Peter Mandelson

Via the opposition whips' office and a stint as shadow civil service minister, Mr Mandelson moved into the foreground of the parliamentary Labour party.

Mr Mandelson had been in the headlines in the last few months after his former aide-turned lobbyist Derek Draper created the "cash for access" row earlier this year by boasting that he could engineer access to senior government ministers.