Just 25% of Irish citizens polled in a survey say they would vote Yes in a referendum on the new EU Reform Treaty.
EU leaders agreed on the treaty text in Lisbon in October
The TNS mrbi poll, commissioned by the Irish Times, indicated a sharp drop in Yes voters compared with a poll on the now defunct EU Constitution in 2005.
Some 62% of Irish respondents said they were undecided on the EU Reform Treaty, agreed in Lisbon last month. The poll showed 13% intending to vote No.
If Irish voters reject the treaty they could throw EU reforms into disarray.
Ireland is constitutionally bound to hold a referendum - and is expected to be the only EU state to do so. The Irish government plans to hold the vote in mid-2008.
All 27 member states have to ratify the new treaty for it to come into force.
Ireland in EU spotlight
The TNS mrbi opinion poll was carried out a week ago with 1,000 adults in all of Ireland's 43 European election constituencies. Support for the Yes camp was strongest in Dublin.
French far-right politician Jean-Marie Le Pen is among the Eurosceptics expected to campaign for a No vote in Ireland.
EU governments are aiming for the treaty to come into force in early 2009.
The treaty retains many of the elements of the ill-fated EU Constitution, which was rejected by French and Dutch voters in 2005.
The treaty aims to streamline decision-making in the enlarged EU of 27 nations.
In 2001 Irish voters rejected the Nice Treaty, which prepared the ground for EU enlargement. But another Irish referendum in 2003 reversed that vote, after the insertion of a treaty clause clarifying Irish neutrality.
The Irish Times says Bertie Ahern's government can draw some comfort from the fact that Green Party supporters appear strongly in favour of the new treaty.
The Greens led the No camp in previous Irish referendums on EU treaties.
The UK, alongside Denmark and the Netherlands, is among the countries whose governments oppose a referendum.
British Eurosceptics want the government to hold a referendum on the treaty, arguing it is no different to the constitution.