(DUBLIN) - Less than a third of Irish people plan to vote for the new European Union treaty in a crunch June 12 referendum, although the vast majority remain undecided, a new poll showed Monday.

The survey, published in the Irish Sun newspaper, found 28 percent have decided to vote "Yes", 12 percent will vote "No" and 60 percent are still to make up their minds.

The referendum will be closely watched across the 27-nation bloc: Ireland is the only EU member state holding a vote, and rejection could in theory stymie the treaty.

In a similar poll last December on the new EU treaty -- which replaces an EU constitution rejected in 2005 -- 22 percent said they would vote "Yes" and 6 percent said they would vote "No" with 72 percent undecided.

The Lisbon treaty was agreed in December 2007 amid much fanfare in the Portuguese capital and aims to prevent decision-making gridlock in the expanding bloc.

An Irish "No" vote in the referendum could topple the blueprint which replaces a European Constitution that was torpedoed by voters in referendums in France and the Netherlands in 2005.

In June 2001 Ireland sent shockwaves through the bloc when it rejected the EU's Nice Treaty on institutional reform and enlargement. That decision was reversed in another referendum in October 2002.

Prime Minister Bertie Ahern announced this month that he will stand down on May 6 to clear his name over claims of financial impropriety, in a move which observers say should draw some fire from the EU "No" campaign.

Few people apparently know what the new treaty means: only six percent fully understand the Lisbon Treaty, while 25 percent had no understanding and 40 percent had very little understanding, the poll said.

The newspaper, which headlines its report "We haven't got a clue", says it is "simply incredible" that so many people don't understand the treaty and, as a consequence, don't know how they will vote.

The pollster interviewed 1,001 adults by telephone between April 7 and 9.

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