The Taoiseach has expressed his "vehement" opposition to the creation of a new job of president of the European Council.
Mr Ahern also said he had no ambition to hold such a position. The new job is one of a number of proposals being put forward for the creation of a new constitution for the EU.
He told the Dáil that the proposed job would create another bureaucracy, "clash" with the EU Commission president, and ministers at the European Council would be "in a sandwich that is not good for Europe".
He was responding during Taoiseach's question time to Opposition leaders who asked his views on the proposals published this week by the Convention on the Future of Europe.
Fine Gael leader Mr Enda Kenny said the next three weeks were "crucial" in shaping a draft document on the future constitution of Europe, which goes for negotiation in the autumn. He asked about the Government's strategy in negotiations, while the Labour leader, Mr Pat Rabbitte, asked about specific changes at the top of the Taoiseach's agenda.
The Green Party leader, Mr Trevor Sargent, called for the Government to "stand firm" on concerns about the election of a president of the European Council.
Mr Ahern said that the proposals published on Monday were one of three parts in total, which were to be published. He broadly welcomed the first part.
However, the institutional part of the proposals, a key component, was omitted and the Government wanted a balance "within the institutions and equality with member-states". If those two issues were maintained, "we are prepared to negotiate on everything else".
Mr Ahern said that if there was a president of the European Council, he or she "will immediately set up an alternative bureaucracy". This might not happen overnight, but "it will happen over a number of years. They will not use the Commission and there will be a clash between the president of the Council and the president of the Commission. Both will play to the Parliament and it will break what has been a successful position. I have vehemently argued against this position."
Mr Caoimhghín Ó Caoláin, Sinn Féin's leader in the Dáil, suggested that the Taoiseach might have ambitions himself for the job, to which Mr Ahern responded firmly that "I have no such ambitions".
He also said he had been on European Councils for a long time and saw the advantages in how they worked. "I do not want to see a future where people here are in a sandwich that is not good for Europe."
He had also tried "to be as helpful as I can to the Greeks", who currently hold the EU presidency, to get "everyone to narrow down their positions".
Mr Ahern told Mr Joe Higgins (Socialist, Dublin West) that any referendum would normally be held two years after the Intergovernmental Conference finished. Asked about security and defence, the Taoiseach said "we are not in agreement on the issue of mutual defence". For any decision in the defence area, "there will have to be unanimity".
