Gordon Brown: "I believe his credentials are well proven"
Gordon Brown has said Tony Blair is an "excellent candidate" to be the first president of the European Council, at a meeting of EU leaders in Brussels.
But the British PM said his predecessor had not yet declared his candidature and the post will not exist until the Lisbon Treaty has been ratified.
When that happens, the field will open to candidates, he said.
Until the treaty is ratified it is not know whether the job will be high-profile or a low-key chairman's role.
Downing Street sources say Mr Brown told a meeting of socialist European leaders they should "get real" and grasp a unique opportunity to get a "strong progressive politician" as president.
He reportedly said Mr Blair had consistently been a passionate and hard-headed champion for Europe.
At a press conference Mr Brown said the main issues being discussed were the ratification of the Lisbon Treaty and climate change but there were discussions "on the margins" about the appointment of president of the European Council.
He said: "Let me say very clearly that we, the British government, believe that Tony Blair would be an excellent candidate and an excellent person to hold the job as president of the council."
We Britain are supporting Tony Blair's candidature
"I believe that his credentials are well proven, his international experience is well known, his expertise on environmental, economic and security issues is known to everybody throughout Europe as well as known throughout the world."
Mr Brown's comments represent his most enthusiastic support yet for the potential candidacy of Mr Blair, with whom he had a long-running rivalry when he was chancellor.
But he added that Mr Blair had not declared himself as a candidate and there was as yet no agreement that the position be set up.
The Czech Republic has yet to ratify the treaty and EU leaders will be considering whether to offer concessions, to ensure it comes into force.
But Mr Brown said the group of socialist leaders had set up a group to look at potential candidates over the "next few days and weeks".
He said there was a "general view" Mr Blair was a good candidate but added: "There will inevitably emerge other candidates and they will have to be taken into consideration as well."
"We, Britain, are supporting Tony Blair's candidature," he added, which he said would be in the "British national interest".
It leaves people feeling they have not been dealt with honestly and plainly, which of course they have not been
And asked whether European divisions over the Iraq war would hurt Mr Blair's candidature, Mr Brown said while it had been "very divisive" in the past - it was not the main issue in Europe today.
But former home secretary Charles Clarke said Mr Blair's "great strengths are not what the European Union most needs from this new presidential office".
Writing in the Independent, he said the UK needed to repair its relationships with the EU and a "fresh start", which Mr Blair's presidency would make difficult to achieve.
Meanwhile Foreign Secretary David Miliband, who has been touted as a possible candidate for the second job which would be set up by the Lisbon Treaty - that of high representative for foreign affairs - said he was "not available and not a candidate".
Earlier he said Europe needed a "strong voice" as president of the European Council - and denied Mr Blair was a divisive figure in Europe.
But shadow foreign secretary William Hague said those backing the Lisbon Treaty - which the Conservatives campaigned for a referendum on - had argued it was simply meant to streamline European affairs and make them more efficient.
"People of course are going to say: 'Well, if the job is that important, that is a major constitutional change and we should have had the referendum we have all been arguing about for the last few years'.
"It leaves people feeling they have not been dealt with honestly and plainly, which of course they have not been."
There is opposition to Mr Blair's candidacy from some smaller EU states which believe the president should come from a country that uses the euro and is part of the border-free Schengen Agreement. Italian PM Silvio Berlusconi backs Mr Blair.
BBC Europe editor Gavin Hewitt said more might be revealed over the next few days about whether leaders favour a charismatic presidential figure or a less high-profile chairman.
Jean Asselborn, Luxembourg's foreign minister, said Mr Blair was "not the best candidate".
He added: "We have to find the personality that represents all the European politics and that represents something new for the future of Europe after the treaty of Lisbon...
"There is a link between Iraq, Bush and Tony Blair, so it's not easy."
He added: "Sometimes in politics you have to show that you can bring things together and not divide them."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.