DUBLIN -(Dow Jones)- The majority of Irish voters saying they will endorse the new European Union budget-discipline treaty in a public referendum on May 31 is strengthening, providing huge relief to Ireland's governing coalition who had feared early-stage campaigning might favor those urging its rejection, according to an opinion poll to be published Sunday.

The Red C poll for The Sunday Business Post newspaper found that Irish voters will approve the EU fiscal treaty by a majority of 63% to 37%, when those who don't know are excluded.

That majority is higher than the 58% to 42% lead for the yes side in a poll the newspaper published two weeks ago--before the formal start of the month-long campaign. Prime Minister Enda Kenny's governing coalition will draw much comfort from the fact that the French election on May 6 appears not to have boosted those in Ireland, urging voters to reject the compact to protest the austerity entailed by the country's bailout program.

The government appeared to have had a difficult early-stage campaign, Communications Minister Pat Rabbitte said in an interview late Friday, because he believed the no side had "misrepresented" the pledge of French president-elect Francois Hollande to re-engineer the compact.

Ireland is only one of the 25 countries participating in the fiscal union--the U.K. and the Czech Republic are staying on the sidelines--whose constitution requires the public passing of the treaty in a referendum.

The treaty will go ahead even if Irish voters were to reject it, Kenny has said, meaning that the Irish would have no second chance to change their minds in any re-run vote.

The newspaper also said that 53% say they will vote yes, 31% say they will vote no, while 16% remain undecided.

"When undecided voters are excluded, the yes side's lead is commanding, with just two and a half weeks to go to polling," said Pat Leahy, the newspaper's deputy editor. "The no side needs something dramatic to change in the campaign if it is to stop the treaty being passed."

The Irish could use the opportunity of the vote to reject the austerity of the country's EU and International Monetary Fund bailout, political analysts have said.

However, Kenny has warned that rejection will cut Ireland off from accessing new bailout funds from the permanent European Stability Mechanism--if it were ever to need such funds in the future--and harm the country's fragile economic recovery.

His government aims to get back to full market funding before the end of next year, when the EU and IMF loans expire.

Opponents of the treaty have dubbed it the "austerity treaty" because it sets stricter oversight on governments to control budget deficits.

But Sinn Fein, the opposition party led by Gerry Adams, which is leading the no campaign, has increased its support to 21% of voters, its highest ever in a Red C poll, the newspaper said.

Fianna Fail, the largest opposition party but which supports the treaty, has the support of 19% of voters, up two percentage points, according to the poll.

Support for Fine Gael, the bigger governing party led by Kenny, is 29%, down three percentage points from the previous Red C poll, while Labour, the junior coalition party, has the support of 13% of voters, down one point on the previous poll.

-By Eamon Quinn, Dow Jones Newswires; +353 1 6762189; eamon.quinn@dowjones.com