A succession of countries cast doubt on Mr Blair’s chances of winning enough support to be nominated as the first President of the European Council as a two-day EU summit opened in Brussels.

France and Germany, who could hold the key to the selection of the new President, also appeared to be cooling in their earlier enthusiasm for Mr Blair’s candidacy.

However, the prospect was growing of the United Kingdom landing the consolation prize of the new post of EU High Representative – effectively its Foreign Minister – with a surprise new British contender emerging for the position. The former cabinet minister Baroness Cathy Ashton, the European trade commissioner, is being championed for the job by both EU diplomats and David Miliband, the British Foreign Secretary.

After Mr Brown’s Eurostar train arrived in Brussels, the Prime Minister travelled straight to a meeting of European socialist leaders to press the case for Mr Blair. He argued that Mr Blair was an excellent negotiator and a passionate pro-European. Mr Brown told them: “You need to get real – this is a unique opportunity to get a strong, progressive politician to be the President of the council.”

Germany’s Sueddeutsche Zeitung newspaper reported last night that during the meeting, Gordon Brown engaged in a shouting match over Blair’s candidacy with Martin Schultz, the leader of the Socialist group in the European Parliament.

Shultz has been campaigning against Blair for weeks. He opposes his appointment because of his support for the Iraq war and his decisions not to introduce the Euro in Britain and to keep the country out of the Schengen agreement, which in effect creates a borderless zone between 25 European countries.

Following the meeting of Social Democrat leaders, the Sueddeutsche described Blair’s chances of obtaining the job as “about zero”, adding: “Blair is out of the running. Nobody wants to give him that job.” Angela Merkel was said to be “not particularly ethusiastic” about his candidature.

Later Mr Brown insisted at a press conference: ‘The European agenda for the next five years will be jobs, growth, climate change and world trade. That is the long-term agenda and Tony Blair is well-placed for that.” But the Prime Minister, who disclosed that he had spoken to Mr Blair this week, acknowledged that other candidates would also emerge once the Lisbon Treaty is finally ratified by the Czech Republic, the final nation to endorse the document.

UK diplomatic sources acknowledged that Mr Blair’s chances are waning rapidly, pointing out that the majority of countries in the EU now had centre-right governments who would not instinctively support him. They told The Independent that they had gone into bat for Mr Blair with their “eyes wide open” about his chances of success, but had taken the stance because they believed it would be in Britain’s and Europe’s interests to have him in the job.

Yesterday Spain, previously viewed as a backer of Blair, dealt a blow to his prospects when Prime Minister José Luis Rodríguez Zapatero said: “We socialists aspire to the post of High Representative.” His comments would appear to rule out a candidate from a left-leaning background also landing the top job.

With the powers of the new President still to be defined, Denmark, Finland and Ireland joined the Benelux countries yesterday by declaring that the President should take a largely behind-the-scenes role rather than acting as a world statesman. That position, which is gaining growing support, would also rule out Mr Blair.

Meanwhile, Herman van Rompuy, the Prime Minister of Belgium who is also in the running, echoed widely held objections to the idea of an internationally known politician taking the post. “The future of the EU does not depend on one person, it depends on someone who will help it operate better,” he said. Asked whether he would block Mr Blair’s candidacy, he shrugged and added: “We do not have a veto right.”

Jean Asselborn, the Deputy Prime Minister of Luxembourg – whose Prime Minister Jean-Claude Juncker is another of Mr Blair’s rivals – said, in an interview with ITV’s News at Ten: “There is a link and there will remain a link for the coming generation between Iraq, [President George] Bush and Tony Blair. Sometimes in politics you have to show that you can bring things together and not divide them. There are better candidates than Tony Blair.”

Support for the Dutch Prime Minister Jan Peter Balkenende appeared to grow yesterday when officials revealed that the Dutch are cranking up their lobbying campaign in Brussels. Their a move was rewarded with the backing of numerous Christian Democrats, including the Italian Foreign Minister Franco Frattini, who said Balkenende would be a “good candidate”. The Italians were previously regarded as Mr Blair’s staunchest advocates. The Dutch PM has refused to enter into speculation over his future, telling his parliament yesterday: “I have not yet been asked and I am busy with other issues right now.”

Meanwhile, EU leaders last night agreed a deal that they hope will smooth the way towards the Czech Republic becoming the last country to sign the Lisbon Treaty. During a working dinner they accepted a Czech demand for an opt-out from a human rights charter attached to the treaty. Fredrik Reinfeldt, the Swedish Prime Minister, said there had been no discussion of candidates for the presidency.