Tony Blair has a close relationship with his press secretary

If he does stand down as the prime minister's official spokesman to take a backroom role as director of communications at No 10, it will be the continuation of a move already underway.

Campbell gave up daily briefings to lobby journalists last year to concentrate more on long-term strategy.

It was a move prompted by the fear that he, rather than his boss, was becoming the focus of media stories.

The year before he had been the subject of an unauthorised biography by the Daily Express columnist Peter Oborne.

It paints a picture of a man so close to the heart to government that ministers take for granted his words carry the full authority of the prime minister.

Long working day

The book recounts how when Foreign Secretary Robin Cook's marriage failed, he received a call from Campbell which implied he must decide between his wife and his mistress - to stop the story getting out of hand in the press.

Campbell's working day starts at six in the morning, according to Oborne. After listening to the news for half an hour, he sets off by car for Downing Street from his North London home and has his first telephone call of the day with Mr Blair.

In his office within the hour, he spends two hours preparing for a meeting with No 10 officials to set out the government's agenda for the day.

A transcript of the mid-morning briefing to lobby journalists is sent to all government departments and is said to be "sacrosanct" - all ministers and press officers are expected to keep to the given line.

Pornographic past

Campbell is the son of a Pennine vet who read modern languages at Cambridge, later making money by writing pornographic stories for the men's magazine Forum.

He entered journalism, rising to edit a new newspaper called Sunday Today at the age of 29. But the publication's launch faltered and the experience led him to have a nervous breakdown.

Campbell is said to have come out of the experience less brash, more disciplined and even more driven in his career.

Around that time he gave up alcohol - a step which many colleagues say gives him the advantage of a clear head 24 hours a day to deal with the media.

Move to Blair

In 1994 he took a massive pay cut to move from being political editor of the Daily Mirror to spokesman for Tony Blair, then leader of the opposition.

With the Labour election victory in 1997, he became the prime minister's chief press secretary, setting up a formidable Whitehall machine to put over the government's views and try to control the news agenda.

Most people see him as a superb spin doctor who gives excellent advice on dealing with journalists.

But there have been several embarrassingly high-profile PR failures for the government - notably when Mr Blair was booed by the Women's Institute convention for giving what they saw as an overtly political speech.

Spin backfires

Chancellor Gordon Brown's spokesman Charlie Whelan resigned after some controversial remarks made him, rather than his minister, the focus of press attention.

The same reason may lie behind any decision by Campbell to 'move upstairs' at Number 10.

And as if to prove it, just look at the news agenda of the day - Campbell's future has pushed off the front pages a major speech to a teachers' conference by the prime minister himself.