EU leaders are said to be furious that the Czech Republic is planning to delay signing the Lisbon treaty for up to six months even if the Irish vote "yes" in their referendum next month.

The country might even try to delay it until after the British general election campaign when a Tory victory would see the question put to voters by David Cameron.

Nicolas Sarkozy, who helped to draw up the treaty after the French and Dutch voted against its predecessor, the EU Constitution, has warned Prague that it faces "consequences" if it does not swiftly follow an Irish "yes" with its own ratification.

The outburst followed a private warning from Jan Fischer, the Czech caretaker Prime Minister, to his EU counterparts over dinner at their summit in Brussels last Thursday, it has emerged.

Mr Fischer said that Václav Klaus, the country's unpredictable President, was planning to have a group of loyal senators in the Czech Upper House refer the treaty back to the country's constitutional court for a second time, which could delay ratification for between three and six months.

This would mean that the treaty could still be unratified going into the British general election campaign, expected next April or May. Mr Cameron has pledged that, if the document remained a live issue, even though Britain has completed its own ratification, he would call a referendum on it. This prospect horrifies most EU leaders, given the strong vein of euroscepticism in Britain.

Tensions are already running high among EU leaders over whether the Irish will vote in favour of the treaty on October 2 after a close-run referendum campaign. They are desperate that the momentum of a "yes" is not lost on the eurosceptic Czech and Polish presidents, the final two signatures required for EU ratification.

The treaty further erodes national powers to veto EU decisions, and a Tory government would campaign against it. President Klaus is understood to have told allies that he wants to wait if possible to see if Mr Cameron wins the next election.

Speaking after last Thursday's dinner, Mr Sarkozy said: "I stated clearly that if the Irish say 'yes', there is no question that we will accept to stay in a no-man’s land with a Europe that does not have the institutions to cope with the crisis,” he said.

Asked about what could be done to persuade President Klaus to sign, he added: "It will be necessary to draw the consequences — but those will be the subject of another meeting."

Mr Fischer is acting as caretaker Prime Minister after the Government of Mirek Topolánek fell in the summer and while fresh elections are organised. He has warned privately that he has little control over the country's headstrong President. Speaking to Czech journalists after last week's summit, he admitted: "It is certainly a fact that several government leaders perceive the ratification process in the Czech Republic with a degree of nervousness."

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