The prime minister is reported to have made clear he intends to serve a full third term in office if re-elected next year.

The Times claims "close Cabinet friends" have been told by Tony Blair that he has no intention of stepping down shortly after the general election, as has been widely speculated recently.

A minimum of 12 years in Downing Street would make him a longer serving premier than Margaret Thatcher, who Blair once said had gone on too long.

And it would frustrate chancellor Gordon Brown who is thought to expect to take over at Number 10 after an early EU constitution referendum in a Labour third term.

But reports suggest the move could be designed to quell rumours of a deal between the two and head off Conservative criticism along the lines of their "vote Blair, get Brown" campaign.

Health secretary John Reid, a key Cabinet ally of Blair, told the BBC on Thursday that it was "not a news story".

"Tony Blair is the most successful leader of any party this country has ever had," he said.

"God and the electorate willing, he has always intended to lead us through a third term."

Amid speculation that the story had been spun by Number 10, Downing Street denied that any minister had been ordered to make the intervention.