Prime Minister Tony Blair insisted he was "absolutely fine" last night after hospital treatment for a recurring heart problem.

A smiling Mr Blair returned to 10 Downing Street earlier than expected following the two-and-a-half hour procedure.

The Premier's irregular heartbeat was corrected and his chances of suffering the problem again were very low, medics said.

Mr Blair first suffered an irregular heartbeat last year, and the condition recurred in August after one of the most difficult periods of his Premiership.

He was sedated while he underwent a catheter ablation - a simple technique used on thousands of UK patients each year.

He will recuperate over the weekend before returning to his desk on Monday and pressing ahead with a visit to Africa next week.

Before being admitted, Mr Blair tried to head off questions over his future by insisting he will, if elected, serve a full third term and then stand down.

But the dramatic declaration sparked fierce speculation about a long and public battle to succeed him.

And Mr Blair's purchase of a luxury London home fuelled doubts that he will see it through to his chosen departure date.

Conservatives said the announcement turned Government into a battleground for potential Labour leaders.

Heir-apparent Gordon Brown reportedly knew nothing of Mr Blair's plans as he set out for IMF and World Bank meetings in the US.

Speaking from Washington, the Chancellor said: "Our thoughts are with Mr Blair, and his family, for the recovery that I think everybody hopes he will have from this operation."

However, tension between the pair has arisen again after the recent return of Darlington MP Alan Milburn to the Cabinet.

The Blairite former health secretary, seen as a potential leadership challenger, has also been handed Mr Brown's role as election supremo.

Announcing his intentions in a series of TV interviews, the PM insisted the Chancellor was still very capable of finally succeeding him at the end of his third term.

However, by marking the finishing line in the race to succeed him, Mr Blair is widely seen as having made it easier for rivals to trip up front- runner Mr Brown.

Close confidant Peter Mandelson said he acted to "bring Labour's own Downing Street version of Neighbours to an early halt".

While backing Mr Brown for the leadership, Deputy Prime Minister John Prescott acknowledged the field was now much wider.

"Tony, unusually, has now put a timetable on it, so that will excite the minds of some people, who many consider to be candidates, as well as the media," he said.

"Of course, Gordon Brown would make a good leader. I could think of other colleagues, but if you ask me about Gordon, no doubt about it."

Former Labour deputy leader Lord Healey, a supporter of the Chancellor, said Mr Blair had made a mistake in declaring his ambitions and should stand aside now in favour of Mr Brown.

"He would almost certainly be pushed out by his own supporters, as Maggie Thatcher was, if he tried to go on for a full five years," the peer said.

Tory Party co-chairman Dr Liam Fox said Mr Blair's announcement would destabilise the Government.

"Up until now we just had a two-horse race, Tony Blair and Gordon Brown, debilitating and paralysing this term of Labour office," he said.

"Now we are going to have the entire Cabinet under starter's orders in the next Parliament, and that is going to be very destabilising - a perpetual war of succession.

"And it means that the Labour Party's personal ambitions will be put before the ambitions of the British people, and that would be tragic."