The Taoiseach Mr Bertie Ahern tonight said the Treaty of Nice - rejected in Thursday’s referendum - could not be renegotiated.
Speaking in the face of intense and angry criticism from opposition parties over the way he had handled the plebiscite campaign, he maintained: "The treaty cannot be undone in any way."
The Government's embarrassment over the referendum result deepened with confirmation that the Minister of State for Agriculture, Mr Eamon Ó Cuív, was among the 54 per cent of the electorate who voted against the treaty.
Mr Ó Cuív claimed afterwards he had acted "as a citizen" and remained a supporter of cabinet policy.
Mr Ahern has infuriated opposition groups - who, together with the coalition government parties urged a Yes vote in the referendum - by refusing to take disciplinary action against Mr Ó Cuív.
He told the Dáil tonight, the Government was taking a long look at the referendum vote on the treaty and said there would be no hasty decisions.
"We have to look at all the options and take into account the reasons why people voted against and examine those issues to see how we can build a strategy to deal with the position."
He said the Government will set up a forum to consider Ireland’s position on EU developments, and the democratic legitimacy, transparency and effectiveness of the EU.
He told the Dáil the forum would be representative of the political parties and the social partners and would be modelled on other bodies such as the forum for peace and reconciliation.
Later this week Mr Ahern will face other EU leaders, for the first time since the referendum, at the European summit in Gothenburg, Sweden.
Mr Ahern made his comments today after a series of meetings in Luxembourg between the Minister for Foreign Affairs Mr Brian Cowen and his counterparts from the applicant states.
The atmosphere at the discussions was later described as "polite - but frosty" with ministers making the point that their entry into Europe has now been seriously delayed.
Mr Cowen repeated the Government’s insistence that the vote did not reflect Irish resistance to expansion of the EU, but was caused by concern among sections of the electorate over the consequences for Ireland's traditional policy of military neutrality.
The Minister will continue his diplomatic offensive and damage limitation exercise in Dublin tomorrow when he has further talks - this time with the ambassadors to Ireland of the applicant countries.
PA