LONDON, June 12 (Xinhua) -- Irish voters are going to the polls on Thursday for a referendum on the European Union (EU)'s reform treaty, the Lisbon Treaty.

    The treaty replaces the failed EU constitution, which was rejected by voters in France and the Netherlands in 2005.

    Ireland is the only one of EU's 27 member states to hold a referendum on the treaty. The plan is for all 27 states to ratify the treaty by the end of this year.

    There are 3 million registered voters in Ireland. Latest polls show that the vote could be a close call of 3 to 5 percentage points favoring a "yes" vote, with about a quarter of voters are still undecided.

    Supporters pin on the economic benefits Ireland has enjoyed in the EU, both from subsidies and immigration from new member states.

    Opponents argue that with more policies to be made through majority voting instead of unanimity, the Lisbon Treaty will weaken Ireland's voice in Europe as well as its neutrality.

    Under Irish law, any amendment to EU treaties requires an amendment to the Irish constitution, and all constitutional amendments require approval by referendum.

    All other 26 EU members will have to ratify the treaty through their parliaments, although in Britain, opposition parties are also demanding a referendum as stipulated in ruling Labor's manifesto.

    So far, 15 countries have ratified the Lisbon Treaty. And a "no" vote in Ireland could scrap the Lisbon Treaty.