The President of the Czech Republic has no intention of signing the Lisbon treaty, a move that might allow David Cameron time to hold a British referendum on Europe.

President Klaus, the fiercely Eurosceptic Czech leader, is the last obstacle for the agreement after its ratification in the other 26 EU states but he has told supporters that he will never sign, The Times has learnt.

Asked during a walkabout on Sunday not to put his name to the treaty, Mr Klaus replied: “Don’t worry, I won’t.”

After a crisis Cabinet meeting yesterday, Jan Fischer, the Czech Prime Minister, avoided a direct confrontation with Mr Klaus, bowing to his demand to reopen negotiations with the EU on an eleventh-hour opt-out.

However, he called on the unpredictable President to guarantee his signature if EU leaders agreed to his conditions and if the Czech Constitutional Court raised no new objections.

Mr Klaus is demanding an opt-out for the Czech Republic that would prevent German families expelled after the Second World War from lodging property claims at the European Court of Justice.

He raised the stakes on Friday, putting a dampener on EU celebrations over the Irish referendum decision to back the treaty. The President argued that the charter could whip up an avalanche of property claims from German families expelled from Czech territory after the war.

Mr Fischer’s refusal to face down his President now throws the problem back at EU leaders at their summit in Brussels on October 29-30, when they had hoped to celebrate the completion of the treaty.

They had also hoped to appoint the EU president and foreign minister, roles created by the treaty, but will now have to be content with a discussion about candidates, including Tony Blair.

The treaty has been passed by both Houses of the Czech parliament but the Prime Minister, acting in a caretaker role after the collapse of Mirek Topolanek’s Government in May, ruled out any attempt to bypass the President.

“I would not like to talk about constitutional crisis,” Mr Fischer told The Times. “The Government is in a position to negotiate the extra conditions revealed by our head of state. We are ready to go to the European Council to put it on the table.”

Hinting at a breakdown in relations between himself and President Klaus, he added: “The Government would like to have clear and sound guarantees from the side of the head of state that this is actually the last step from his side and no other additional conditions will be added.”

Mr Fischer, who will be in Brussels for talks today, said he hoped that the treaty could still be concluded by the end of the year. The lack of agreement from Mr Klaus will infuriate other EU members, particularly France and Germany, which are pushing hard to wrap up the Lisbon treaty saga.

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