Downing Street has played down reports that Alastair Campbell is to quit as the government's director of communications.
Will he go or will he stay?
It said claims made by the BBC that he had agreed to leave after the publication of Lord Hutton's inquiry into the death of the government scientist, Dr David Kelly, were "wishful thinking".
Culture Secretary Tessa Jowell has also mounted a strong defence of Mr Campbell's record in government, describing him as having been "a great force for good".
Number 10 made the remarks after BBC political editor Andrew Marr said Mr Campbell had spoken to Mr Blair about his future on Thursday.
During the meeting the pair agreed that to leave before the inquiry reported its findings might be interpreted that Downing Street had done something wrong, Marr said.
But the prime minister's spokesman said: "The BBC's political editor has not spoken to Alastair Campbell about this.
"It is another example of the BBC fixing on gossip rather than substance. The main issue remains that the BBC broadcast unsubstantiated allegations and we stand by our position on this matter which will be examined by the Hutton inquiry."
But Marr said that was "disingenuous" of Downing Street.
"Alastair Campbell knew perfectly well what I was going to broadcast yesterday and had spoken to another press officer and authorised that press officer to speak on his behalf," Marr told BBC Radio 4's Today programme on Friday.
And a BBC spokesman said: "We stand by Andrew Marr's report."
Marr said: "I am in no doubt at all, that as we are now, Alastair Campbell is determined to go, that the prime minister knows that and has agreed that.
"Of course, everybody is human, people can change their minds, but at the moment he is certainly going this year."
Marr said depending on how long the Hutton Inquiry took, Mr Campbell could leave Downing Street by autumn.
Mr Campbell believes he will be vindicated by the inquiry, Marr said.
His departure would mean a radical rethink of the way New Labour deals with the media, according to Marr.
Mr Campbell has been one of Mr Blair's closest allies
Mr Campbell was "a large and vivid presence", said Marr, adding: "Life will be a little duller without him."
Shadow foreign secretary Michael Ancram said: "If he decides to go, as far as I'm concerned, [it's] not before time."
Ms Jowell said she did not know Mr Campbell's plans, but stressed that he was "a person of extraordinary talent who has been a great force for good in the government since 1997".
"Alastair's decision is a decision for Alastair in discussion with the prime minister. It is not a decision that should fill the air waves with gossip obsessed speculation ..." she told BBC's World at One programme.
"Alastair Campbell is a strong man, a good man and a person who in every fibre of his body believes in Labour values."
But she warned that politics must move away from "aggressive, macho engagement" and argued that both the government and the BBC needed to prove they deserved people's trust.
If Mr Campbell, a former Daily Mirror political editor, does resign it would be a blow to Mr Blair.
Mr Campbell, one of the small group of people credited with creating New Labour, has been at Mr Blair's side since he became Labour Party leader in the early 1990s.
He is believed to have wielded great influence over Mr Blair - so much so that he was often referred to as the "real deputy prime minister".
Over the past month Mr Campbell has been locked in a war of words with the BBC over its report claiming that Downing Street had "sexed up" September's dossier outlining the threat from Iraq's weapons of mass destruction.
The source for the BBC's report was weapons expert Dr Kelly, who was found dead last Friday.
Mr Campbell has vehemently denied inserting into the dossier a claim that Iraq could launch weapons of mass destruction within 45 minutes.
And the media chief was cleared by the Foreign Affairs Select Committee of the "sexing up" charge.
Mr Campbell's key achievement in opposition was to turn an overwhelmingly anti-Labour media into one that mostly supported New Labour at the 1997 election.
Once in Downing Street he took the daily briefings of political journalists and led a public relations machine which succeeded in maintaining a largely good press for his boss's government right through to the 2001 election victory.
But as the backlash against New Labour "spin" grew, Mr Campbell took a more backseat role, no longer doing the daily briefings.
It has been widely reported that his partner, Fiona Millar, is also stepping down from her role as Cherie Blair's chief of staff.