Tony Blair is in line to be proclaimed Europe’s first president within weeks if the Irish vote “yes” in today’s referendum.

Senior British sources have told The Times that President Sarkozy has decided that Mr Blair is the best candidate and that Angela Merkel has softened her opposition.

The former Prime Minister could be ushered into the European Union’s top post at a summit on October 29.

Ms Merkel, the German Chancellor, was opposed to Mr Blair because she believed that the post should go to a country that had adopted the euro but British sources said that she may now be “biddable” if Germany and France get plum posts in the new European Commission.

German sources insisted that it was far from clear that Ms Merkel had changed her mind and there were suggestions in Paris that Mr Sarkozy was happy to be seen to be backing Mr Blair because he knew that Ms Merkel would scupper the appointment.

Mr Blair, whose claims are being advanced by ministers in London, will not enter the race unless he is certain of winning. He is wary of giving up his many other commitments, spanning business, the Middle East, climate change and his Faith Foundation.

If the Irish ratify the Lisbon treaty — the result will be declared tomorrow — only the signatures of the Polish and Czech presidents will be needed for full ratification. Warsaw is expected to come on board swiftly. President Klaus is harder to predict but diplomatic sources expect him to agree quickly, possibly after receiving a sweetener from Germany.

The decision presents a dilemma for the Conservatives, whose conference takes place next week. David Cameron remains committed to a referendum on the treaty. He has declined to say what he would do if the treaty were ratified before the general election.

Despite pressure from Eurosceptics, he would be unlikely to hold a referendum if he came to power after ratification, which would mean renegotiating Britain’s relationship with the EU, but a Europe with Mr Blair at its head would worry Tories even more.

Ms Merkel has touted Jean-Claude Juncker, of Luxembourg, for the role, but the backroom dealer would hardly set European pulses racing. It is understood that President Sarkozy proposed Felipe González, of Spain, privately to Ms Merkel, but that she was suspicious of endorsing the Socialist.

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