BRUSSELS, June 12 (Xinhua) -- The European Union (EU) welcomed the ratification of the Lisbon Treaty by the Greek Parliament on Thursday morning.

    "I would like to congratulate Greece on the successful approval of the Treaty of Lisbon by the parliament earlier this morning. I want to thank the Greek government and parliament for their unwavering support for the European Union and the new treaty," said European Commission President Jose Manuel Barroso in a statement.

    The Lisbon Treaty, signed by EU heads of state and government last December in the Portuguese capital Lisbon, was expected to replace a failed EU constitution designed to streamline the policies of the 27-nation bloc and improve its efficiency in dealing with future challenges.

    The entry into force of the treaty requires the ratification of all 27 EU member states. So far, 18 have approved the document through the parliamentary process.

    Irish voters went to the polls on Thursday for a referendum on the treaty. As Ireland is the only EU member state to hold a referendum, the Irish vote is crucial to the fate of the treaty.