The majority of Irish people do not understand the European Union's reform treaty only weeks before voters determine its fate in a national referendum, a poll showed.
Ireland is the only EU state planning a referendum on the treaty, meaning that a "no" vote on June 12 from one of Europe's smallest countries could sink the project designed to end years of diplomatic wrangling over reform of the bloc's institutions.
A poll of 500 people by Ireland's independent Referendum Commission found 62% said they did not understand the treaty at all.
The survey by the commission, which was set up to inform Irish people about the treaty and encourage them to vote, found only 5% understood the accord quite well or very well.
"The research ... shows the level of public understanding of the treaty right now to be quite poor," its chairman Iarfhlaith O'Neill told reporters.
Outgoing Irish Prime Minister Bertie Ahern, who will step down on May 6, said on Sunday failure to back the Lisbon treaty would be a "disaster" for Ireland.
A separate poll over the weekend by Ireland's Sunday Business Post newspaper showed a drop in support for the "yes" camp with 35% saying they would back the treaty, down from 43% canvassed in February.
Those who planned to vote "no" rose to 31% from 24% previously. Those who were undecided reached 34% from 33% in February.
O'Neill said the commission would begin its public awareness campaign in the coming weeks about the treaty, which replaces an EU constitution rejected by French and Dutch voters in 2005.
But concern is growing that the treaty could be a focus for issues such as taxation, which could mobilise opposition to it.
Ahern said this month a debate over whether the EU should harmonise the way corporate taxes are computed was damaging the chances of securing backing for the treaty.
European Commission President Jose Manuel Barroso visited Dublin this month to reassure voters Ireland would continue to have a veto on taxation proposals. His trip followed one by German Chancellor Angela Merkel, who urged a "yes" vote.