The latest opinion poll shows a dramatic swing against the Lisbon Treaty, with the Yes side leading by just 6% when those undecided are excluded.
The Red C poll in tomorrow's Sunday Business Post has been welcomed by anti-Lisbon campaigners, while the Government says the result is disappointing, but not entirely surprising.
Up to now, opinion polls have suggested a two to one majority in favour of the treaty.
The poll says that among those entitled to vote, 35% are backing the treaty, a fall of eight per cent since the last poll two months ago.
31% are opposed to Lisbon, an increase of seven points, while one third of voters, 34%, do not know.
When those undecided are excluded, the Yes side leads by 53% to 47%, a very narrow margin with seven weeks to go to polling.
The change in opinion is particularly marked among farmers, according to Red C. Irish Farmers Association President Padraig Walshe said this was not surprising as his members are very worried about the position being taken in the World Trade talks by EU Commissioner Peter Mandelson.
Dick Roche, the Minister for European Affairs, said the political campaign will get under way once the referendum bill is through the Oireachtas, and that it is all 'very much to play for'.
Anti-Lisbon group Libertas welcomed the findings, and said its concerns over taxation, democracy and accountability are resonating with the electorate.