Revelling in the fuss he was causing, Vaclav Klaus, the president of the Czech Republic, calmly tucked into a plate of steamed shellfish on the terrace of the elegant Adriatic hotel in the Albanian seaside resort of Durres last week.

In faraway Brussels furious diplomats were calling for his impeachment and even his country’s expulsion from the European Union because of his obstinate refusal to sign the Lisbon treaty. Klaus, now the only European leader holding out against ratifying the document, made it clear he did not give a damn.

European leaders were told he was not available to take their calls. The Eurosceptic president and his wife Livia were completing a brief tour of the Balkan country where Klaus, 68, attended the launch of the Albanian edition of his controversial book, Blue Planet in Green Shackles, which argues there is no such thing as man-made global warming.

The trip had clearly been planned to coincide with the diplomatic blitz that Brussels launched after last weekend’s referendum in Ireland, which appeared to remove the final hurdle to ratification. Klaus seemed to have other ideas.

Lech Kaczynski, the Polish president, left Klaus further isolated by signing the treaty into law yesterday. “The EU remains a union of nation states, a strict union, and let it remain so,” Kaczynski said.

Calling the organisation “a successful experiment without precedent in human history”, he said it could not be closed to those who wish to join, “not only in the Balkans but also countries like Georgia”.

On Klaus’s return to Prague he dropped a political bombshell. At a press conference in his official residence the Czech leader announced that he would sign the treaty only if his government negotiated an opt-out from the Charter of Fundamental Rights, which is incorporated in the treaty.

He was concerned that the charter may permit retrospective property claims by the Sudeten Germans, a 3.5m-strong minority group expelled from the Czech Republic after the second world war.

“I have always considered this treaty a step in the wrong direction,” Klaus said. As he is well aware, the slightest change to the treaty, which was first proposed in 2001, would require all 27 EU member countries to agree.

His remarks were greeted with outrage in Europe. German and French diplomats, in talks with their Czech counterparts, explored two ways of removing the Klaus obstacle: impeach him or change the Czech constitution to take away his right of veto.

“If the president is obstructing the democratic process and opposing the decision of parliament as well as the will of the people, he is moving beyond the law and will need to face the consequences,” a German diplomat told The Sunday Times.

Jiri Oberfalzer, a member of the Czech senate and Klaus’s closest ally, said Nicolas Sarkozy, the French president, had already threatened the Czechs with expulsion from the EU.

“Ideas of changing the constitution just to get rid of the president only shows how weak our young democracy is,” said Oberfalzer, a Eurosceptic.

The political hot potato now lands in the hands of the caretaker government of Jan Fischer, the prime minister.

Under the Czech constitution a president can be impeached only if he commits high treason against the country’s independence or its territorial integrity and democratic order. It is highly unlikely that parliament would pass such a measure under Fischer’s interim government.

There are other hurdles. The treaty has been approved by the Czech parliament but senators loyal to Klaus have lodged three challenges with the constitutional court, which has rejected two and is widely expected to follow suit with the third.

Opponents of the treaty hope that Klaus will be able to stall ratification until the British general election in May. David Cameron, the Tory leader, has promised a referendum if his party wins and the treaty is still unsigned.

Klaus is unlikely to give in without at least some concessions. He is said to want to be seen as the leader who derailed the European project. A comparison is being drawn in Prague with Edvard Benes, the pre-war Czech leader who in 1938 had to flee to Britain after refusing to cede territory to Hitler under the Munich agreement.

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