(DUBLIN) - Irish Prime Minister Bertie Ahern warned Sunday that it would be a disaster for Ireland to reject the European Union's key Lisbon Reform Treaty in a referendum on June 12.

He commented after a newspaper poll showed the government's campaign for a "Yes" vote had suffered a significant setback.

A Sunday Business Port/Red C poll show a substantial shift in public opinion against the treaty with the number planning to vote "Yes" dropping to 35 percent, down eight percentage points on a similar poll two months ago.

Some 31 percent of Irish citizens said they would vote "No", an increase of seven points. The number of undecideds had increased by one point to 34 percent.

The swing against the treaty is particularly marked among farmers and Ahern warned a "No" vote "would have repercussions that would severely damage us".

"The biggest beneficiaries (of the EU) are the agricultural community," he told RTE state radio. "They should be the ones leading this campaign for it (the treaty)."

"I just hope that the agricultural community quickly turn around their attitude and get behind the Lisbon agenda," he said.

Ireland is the only one of the 27 EU nations planning to hold a referendum on the treaty, and a "No" vote could scupper it altogether.

In 2001, Ireland shocked the EU when it rejected the bloc's previous Nice Treaty on institutional reform and enlargement. That decision was reversed in another referendum.

A planned EU constitution was scuppered by voters in France and the Netherlands in referendums.

Ahern retires on May 8 and with seven weeks until the June 12 vote, his successor, Finance Minister Brian Cowen, will have to campaign hard if the government is to regain the initiative.

When European Commission President Jose Manuel Barroso visited Dublin this month to back the treaty, over 10,000 farmers gridlocked Dublin's streets in one of the biggest shows of force in a decade.

They were demonstrating against the EU stance in talks over a world trade deal, claiming it would damage Irish agriculture.

The poll was conducted on Monday, Tuesday and Wednesday of last week, among more than 1,000 voters across the country.

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