Taoiseach Brian Cowen has dismissed suggestions that the Government has failed to explain the Lisbon Treaty.
Speaking in Galway, Mr Cowen accused No campaigners of creating confusion around the the Treaty.
Almost 33% of No voters responding to a poll in today's Irish Times, said they were voting against the Treaty because they did not understand it.
Mr Cowen said he is not overly concerned with the Lisbon Treaty new poll results, but warned that a No vote will damage Ireland's political reputation.
With six days to go to polling day, the TNS mrbi poll in today's Irish Times showed opponents of the treaty taking a five-point lead over those who support it.
Speaking on RTÉ Radio's Today With Pat Kenny this morning, Mr Cowen said there was no validity to the main points being raised by the No campaign, who he accused of creating fear, suspicion and confusion.
He said those backing the treaty had further work to do but he was confident the Yes vote would increase.
Declan Ganley, the founder of Libertas, which opposes the treaty, said the results of the opinion poll should be taken with a grain of salt. He said the referendum was still there for the taking by either side.
Mr Ganley, meanwhile, has accepted a challenge from the Minister for Health, Mary Harney, to a debate on the economic implications of the document.
Ms Harney said a Yes vote was Ireland's best option for investment and jobs in the future.
In response, Mr Ganley said he looked forward to a debate on what he claimed were the potentially disastrous implications of Lisbon for inward investment into Ireland.
The Minister for Finance has said there is no plan B if the Lisbon Treaty is rejected, as suggested by those opposed to it.
Speaking on RTÉ Radio's Morning Ireland, Mr Lenihan said supporting the treaty was vital for Ireland's interests.
He said every citizen needed to take direct responsibility for their place in a progressive Europe.
Also on the programme, Sinn Féin MEP Mary Lou McDonald said the poll showed that the Irish public believed a better deal was possible.
Minister for Foreign Affairs Micheál Martin, who is the director of Fianna Fáil's campaign, said the poll showed that there was still a lot of confusion because much of the debate to date has focused on issues that are not in the document.
Mr Martin said in the past, polls taken over a week before voting have not always proved accurate in predicting the final result.
The pro-treaty organisation, the Alliance for Europe, which is chaired by Ruairí Quinn, has said that while it was disappointed with the poll, it believed the referendum still could be won.
TNS mrbi interviewed 1,000 voters throughout Ireland on Tuesday and Wednesday, and found that 30% said they would vote Yes. This is a fall of five points since the last poll three weeks ago.
But opposition to the treaty is up 17% to 35%. The number of people who are undecided has fallen 12% to 35%.
Opinion polls up to now in the referendum campaign had indicated support for the Lisbon Treaty.
PANA opposes Irish role in EU defence policy
Meanwhile, the Peace and Neutrality Alliance has claimed that the Lisbon Treaty would lead to Irish involvement in European defence policy.
Although the proposed wording to be put into the Constitution specifically precludes Ireland from joining any common defence set up under the treaty, PANA claims Lisbon would lead to greater involvement in defence policy.
PANA Chairman Roger Cole said 'the devil is in the detail'.
At a news conference in Dublin, the organisation was critical of the Referendum Commission claiming it had not given the full facts in its leaflet explaining the treaty.
RTÉ.ie/Lisbon has complete coverage of the Lisbon Treaty