Minister of State Martin Mansergh has rejected claims by those opposing the Treaty of Lisbon that a better deal could still be negotiated.
He told a public meeting in Clonmel that in his opinion there was no possibility of unilaterally or multilaterally re-opening the compromises reached after long and arduous negotiations.
Cóir, a group opposed to the treaty has meanwhile accused the Fine Gael leader, Enda Kenny, of a being dishonest in allegedly stating that it would not endanger Ireland's protection of unborn children.
The group challenged Mr Kenny to a debate on the issue.
Earlier, the Sinn Féin President said that the Lisbon Treaty was not as complex a document as has been claimed, and said that the Yes campaign was scaremongering by exaggerating the consequences of its rejection.
The comments made by Gerry Adams at the launch of the party's campaign against the treaty have been rejected by Labour.
Sinn Féin says that those in favour of the Lisbon Treaty would like the electorate to think that rejection would mean the end of the world.
Speaking in Dublin, the party's leader said that the document was not 'rocket science' as he put it and that what was needed was a rational debate on the issues.
The party's MEP, Mary Lou McDonald, told the launch that rejection would lead to the negotation of a better alternative, claiming that the current document was dangerous for the Irish economy and for the agricultural sector.
But that view was rejected by Labour's Eamon Gilmore, who insisted that the voters would have to decide next month on the treaty before them and not some vague alternative that had yet to be framed.
Separately, Fine Gael front bench spokesman Leo Varadkar has claimed that John Gormley has risked disenfranchising thousands of voters by waiting two days before the postal vote deadline to advertise the register.
Mr Varadkar said up to 50,000 people could be affected by the fact that advertisements asking people to apply for postal votes were placed last Monday while the register closed the following Wednesday.
But a spokesman for the Environment Minister said this evening that the advertisements were placed at the earliest possible opportunity in what was a very tight legal deadline.
He confirmed that the situation regarding applications for postal votes would be addressed in the context of the planned electoral commission, which would be taking responsibility for a range of matters.
Rock the Vote reaches out to young voters
This morning, a campaign was launched to encourage young people to make their voices heard in the Lisbon Treaty Referendum.
Rock The Vote aims to promote political engagement among first time voters and those in their 20s.
Last year, Ireland got its first taste of the initiative in the months leading up the General Election but similar voter recruitment drives have been happening in the US for years.
The people behind the campaign say they want to make the issues contained in the Lisbon Treaty crystal clear for young voters and connect with them, in a way that other groups may not be able to.
As well as working with youth groups and student unions around the country, the Internet will be a cornerstone of the effort to increase turnout on 12 June.
RTÉ.ie/lisbon has complete coverage of the Lisbon Treaty.