The fate of the EU’s Lisbon treaty had been thrown into question once again on Thursday after Vaclav Klaus, the Czech president, threatened not to approve special legal provisions for Ireland.

Mr Klaus said the Czech parliament must ratify the guarantees on national sovereignty that Ireland wants in order to hold a referendum on the treaty, or he would not give them the green light.

The Irish guarantees, covering taxation, military neutrality and right-to-life policies, were the first order of business for the EU’s 27 national leaders as they gathered in Brussels for a two-day summit.

The Lisbon treaty, which would create the EU’s first full-time president, streamline the bloc’s decision-making procedures and give more powers to the European parliament, is the culmination of almost a decade of efforts to modernise the EU’s institutions.

Irish voters rejected the treaty in a referendum a year ago, and Mr Klaus and Lech Kaczynski, the Polish president, have refused to sign the document even though their parliaments have approved it.

Mr Klaus’s latest move indicates that he may try to find an excuse not to sign the treaty, even if Irish voters back Lisbon in a second referendum expected in October. Opinion polls in Ireland suggest that popular opposition to the treaty has fallen sharply since the Irish economy’s descent into crisis.

Apart from legal guarantees of sovereignty, Ireland will secure a declaration on the protection of workers’ right and has been promised it can keep a seat on the European Commission.

Mr Klaus contended that the guarantees altered the treaty in such a way that they would require separate ratification by the Czech parliament under the nation’s constitution.

His argument was contested by Jan Fischer, the Czech prime minister. However, Mr Fischer is a non-party, interim premier who, in contrast to Mr Klaus, is unlikely to remain in office after elections in October.

The worst fear of EU leaders is that Mr Klaus delays signing the treaty for so long that a strongly Eurosceptic Conservative party replaces the UK’s Labour government and holds a referendum on Lisbon, resulting in a No vote that would kill it for ever.

…whole article in the FT