Czech President Vaclav Klaus has signed the EU reform treaty.

The Czech Republic was the only EU country not to have ratified the treaty, designed to make Europe a more powerful global player.

Earlier, the Czech constitutional court rejected a complaint against the treaty and ruled it was constitutional.

Court chief judge Pavel Rychetsky ruled the so-called Lisbon Treaty "does not violate the constitution."

Euro-sceptic President Klaus was the final obstacle to the full ratification of the charter, which was bogged down in negotiations for almost a decade but has now been ratified by all 27 EU nations.

EU leaders believe its reforms - creating a new EU president post, giving more power to the foreign policy chief and streamlining EU decision-making - are needed to make the EU more effective.

Last week, they agreed to a last-minute demand from President Klaus - an opt-out from the treaty's Charter of Fundamental Rights - in return for his signature of approval.

The Czech leader, who expressed fears the treaty would hand over too many national powers to EU institutions in Brussels, asked for the opt-out over worries of property claims by ethnic Germans stripped of their land and expelled after the Second World War.

British Prime Minister Gordon Brown said the decision marked "an important and historic step for all of Europe".

He said in a statement: "I welcome President Klaus's decision to sign the Lisbon Treaty, thereby completing the process of ratification in the Czech Republic. Today is a day when Europe looks forward, when it sets aside years of debate on its institutions and moves to take strong and collective action on the issues that matter most to European citizens: security; climate change; jobs; and growth."