Deputy Prime Minister John Prescott has said Cabinet ministers are speculating about their future in the event of Tony Blair deciding to step down.
The interview will increase speculation about Mr Blair's plans
Speaking to the Times, Mr Prescott spoke of "moving plates" and people "repositioning themselves".
Opposition politicians argued Prescott had implicitly sent a message to the premier that it was time to go.
But friends of Mr Blair later told the Observer he would stay at least until Iraq goes to the polls next year.
"His view is 'I got us unto this, I'm not going to walk away while we are still in the middle of it'," an unspecified friend of the prime minister told the paper.
"We have got some important milestones coming up, like January of next year when we have got elections in Iraq," he added.
"Once we got into the autumn I certainly can't see him going, even if things do get worse in Iraq."
'Every PM goes'
In his interview published on Saturday, Mr Prescott compared the possible future political changes to a seismic shift that was yet to come.
"I think it's true that, when plates appear to be moving, everyone positions themselves for it," he said.
"People do talk about it [Blair's succession] and you get that discussion... every British prime minister goes eventually".
He later issued a statement saying the Times' headline "Race to seize Blair's crown is under way", was "untrue".
"Of course there has
been speculation over the leadership, but the reality is there's no race for the
prime minister's position," he said.
But the interview fuelled rumours that Mr Blair was being advised by his closest collaborators that stepping down would be in the interest of Labour.
Tory chairman Liam Fox told ITV News: "We have a weakened prime minister who has been there for over seven years.
"We have an ambitious chancellor who is desperate to get to No 10, the Cabinet ministers manoeuvring for position and a deputy prime minister who is supposedly there to make the peace, but keeps making things worse for them all."
Vince Cable, Liberal Democrat Treasury spokesman, said Mr Prescott, whom he described as "a solid supporter of the prime minister", had sent Mr Blair a clear message:
"When he comes out publicly making this kind of noise, suggesting there is internal disharmony, I think he is trying to send a signal to his boss that his position is very insecure," Mr Cable said.
In the Times, Mr Prescott said relations between Tony Blair and Gordon Brown had broken down early in the life of the Labour government.
He said the prime minister and chancellor had had a "pretty serious breakdown of relations", but stressed that their relationship had improved in recent months.
He added that there had been a "dramatic improvement" after he "bashed their heads together" at a dinner meeting last November, and that they were now working "extremely well" together.
Mr Prescott's comments came after speculation about Mr Blair's future circulated through Westminster, as problems in Iraq cause mounting concern on Labour's backbenches.
Mr Prescott said Mr Blair was on course to win the next general election, expected this time next year - but he stopped short of insisting the prime minister would serve a full third term as head of the government.
On Friday, Mr Blair dismissed reports he was thinking about letting Mr Brown take over as prime minister as "froth".