Irish leader Bertie Ahern has pledged an "enormous national campaign" to try to ensure a "yes" vote on the Nice Treaty, which is hanging in the balance as his popularity crashes in the opinion polls.

Latest surveys suggest that support for Mr Ahern's government has plunged, along with his personal rating, while millions of voters remain undecided on the treaty itself.

Nice Treaty voting intentions

For 37% Against 25% Undecided 32% Not voting 7% Source: Irish Times/MRBI

The "yes" campaign took another major knock last week when its chief architect, PJ Mara, resigned after being named in a report on political corruption.

On Monday the president of the European parliament, Irishman Pat Cox, said he had encountered public anger in his constituency at the weekend when trying to persuade people to vote in favour of ratification.

"I've been saying to people, please try to separate out the issues, the domestic issues, which are very important, and the short-term political questions, from the long-term national interest," he said on Irish radio.

Mr Ahern's comments came as he formally launched the campaign on Sunday to persuade voters to back the treaty when it is put to them for the second time on 19 October.

He acknowledged that a "real tough battle" lay ahead, and confirmed that the large number of undecided voters was a source of disappointment.

Across Eastern Europe people are awaiting our decision

Bertie Ahern

But Mr Ahern insisted that the countries lining up to join the EU deserved Ireland's backing.

"Across Eastern Europe people are awaiting our decision. They want to achieve in their own country what we have achieved for ourselves in Ireland," Mr Ahern said.

"They want to share our experience and repeat the Irish success story."

Irish voters threw out the Nice Treaty, which clears the way for the expansion of the European Union, at the first time of asking, in June 2001.

Rejection headaches

All 14 other EU states have already ratified it.

A second rejection in Ireland would create problems for the current expansion timetable, and would also be seen as enormously embarrassing to Mr Ahern's government.

The latest public opinion test, conducted by the Irish Times newspaper, suggest 37% of voters were planning to accept the treaty and 25% to reject it. A huge 32% of those polled said they had not decided.

Ahern says a tough battle lies ahead

The survey suggests a narrower level of support than ahead of the June 2001 rejection.

Mr Ahern's personal approval rating has tumbled by 19 points to 51%, the lowest since he took over as Fianna Fail leader in 1994.

And backing for his government is down 25 points to 36%.

Public opinion is believed to have been turned against the administration by a number of factors, including leaked plans to cut public spending despite election promises to the contrary.

But worse was to come, when a senior judge heading a corruption tribunal accused Mr Mara of failing to co-operate with the tribunal, by failing to declare a bank account. A former foreign minister, Ray Burke, was accused by the judge of taking bribes in the 1970s and 1980s.

Irish Foreign Minister Brian Cowen, also speaking at Sunday's "yes" campaign launch, urged voters not to reject the treaty as a way to punish the government over recent scandals.

"Some say they should use the vote on the Nice Treaty to send a message about other matters. Some may be tempted to do so. This would be a mistake," Mr Cowen said.