PRESIDENT CHIRAC of France is preparing to throw Europe into confusion and put Britain on the spot by backing moves to keep the European constitution alive if it is rejected in Sunday’s referendum.

French diplomats say that M Chirac is expected to urge other countries to proceed with ratification because France does not want to be seen to be blocking the European project. Any attempt to persuade other countries to go ahead will dash the hopes of those in the British Government who believed that a French rejection would make a British referendum unnecessary.

British ministers argue that it will be impossible to hold a referendum next year because the final shape of the treaty on which the British would be voting will be unknown.

President Chirac was still insisting last night that renegotiation was out of the question if the French vote "no". British ministers believe that the only way that the French could get eventual approval would be to amend the constitution in a way that would make it unacceptable in Britain.

“We do not know if there is going to be a ‘yes’ or ‘no’ but a ‘no’ would create massive uncertainty about what we are supposed to be voting on,” a ministerial source said. M Chirac went on French television last night to deliver a dramatic last-ditch appeal for a ‘yes’ vote. He urged the French people not to punish his Government.

“The decision before us goes far beyond traditional political divisions,” he said. The choice was “about your future and that of your children, of the future of France and the future of Europe. On Sunday, everyone will have a share of the destiny of France in its hands.”

He argued that the constitution would strengthen France’s influence in Europe and reinforce the French social model. Rejecting it would create “divisions and doubts” in Europe when “we need a political Europe capable of bringing about a genuine European power”.

But the latest poll showed the rejectionists’ support growing to 55 per cent — the 13th poll in succession to put the ‘no’ camp ahead. With two days of campaigning left, the French political establishment was left hoping for a Liverpool-style comeback.

Even as M Chirac prepared to deliver his appeal last night the recriminations within his centre-right UMP party had begun, and he was said by colleagues to have accepted that he had bungled by calling a referendum.

A "no" vote would leave M Chirac seriously weakened. His rival Nicolas Sarkozy, the UMP leader who aspires to become president in 2007, was blaming the Chirac Government's policies for fuelling the voter rebellion. M Chirac is expected to react to a French "non" by promising to listen to the people before making a second attempt at ratification.

He and other "yes" campaigners have said repeatedly during the campaign that there is no “Plan B” if the treaty is rejected and that there would not be a second referendum.

But one option being discussed in senior diplomatic circles is for candidates in the French presidential election in 2007 to promise to ratify the treaty in parliament rather than by referendum.

Mr Blair is expected to respond to the French result on Monday morning from Italy, where he is spending the Bank Holiday weekend. He is reconciled to Britain's six-month presidency of the EU, which starts in July, being dominated by efforts to salvage key parts of the constitution if the French and Dutch reject it.

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