Negotiations to review the EU's internal workings will produce an EU constitution, the Connacht/Ulster MEP, Ms Dana Rosemary Scallon MEP has claimed.
"Our Government and political parties can not be trusted to hold out against this agenda especially as they did not respect nor represent the Irish people's democratic rejection of Nice," she said.
Accusing the Government and others of "a concerted conspiracy of silence", she said plans for a constitution were being "openly discussed" at the Convention on the Future of Europe.
In late August, the British government said it would support an EU Constitution, but only if it stated the EU's fundamental principles and clearly divided responsibilities between the EU and member-states.
Before the Treaty of Nice negotiations, the Taoiseach, Mr Ahern refused to accept the Charter of Fundamental Rights unless he was guaranteed that it would never become legally binding.
However, the Connacht/Ulster MEP said the ratification of the Treaty now would open the door to the charter becoming legally binding, and, thus, overriding the Irish Constitution.
"European judges could then be empowered to override any national law or constitutional position that contravened any of the EU laws or rights enshrined in the EU constitution. The transformation of the Union from an association of Sovereign States into a Superstate in its own right would be complete," claimed Ms Scallon, speaking in Dublin.
The Department of Foreign Affairs said the Government was "prepared to look at the idea" of a constitution if it simplified the complex web of existing EU treaties.
In its submission to the Convention on Europe, the British government suggested a past or serving head of government or state could serve as the EU president.
The title-holder would take over the chair of the European Council, rather than having it rotated every six months among the EU's 15 leaders, and represent the Union on the international stage.
However, the British government also wants to use a constitution to limit the power of Brussels by giving national parliaments more power to decide whether key policy decisions should be taken at EU or national level.
In addition, the British government insists that the Charter on Fundamental Rights should not become part of EU law, and that the European Commission should not be given more power over economic and social issues.
In an effort to minimise the Commission's role in foreign policy, the British government said the EU's High Representative on common foreign and security policy, Mr Javier Solana, should remain outside of the Commission's control.