Both the Amsterdam Treaty and the referendum on its ratification "fail the democratic test", according to Sinn Fein.
Calling for a No vote on the treaty, the party's TD for Cavan-Monaghan, Mr Caoimhghin O Caolain, said yesterday the vote was taking place in circumstances that made a truly informed debate impossible.
"The primary reason for this is the inexcusable decision by the Government to hold the referendum on the Amsterdam Treaty and the referendum on the Good Friday document on the same day," he added.
Several surveys showed the majority of citizens did not even know of the existence of the Amsterdam Treaty, which was signed seven months ago. The conclusion of the multi-party talks and the emergence of the Good Friday document had "almost totally eclipsed" the Amsterdam issue.
Accusing the Government and Opposition of confusing the treaty and the Belfast Agreement, Mr O Caolain said they hoped the people would endorse the Amsterdam accord on trust.
Sinn Fein was opposed to the transformation of sovereign states into "one big state". It was fundamentally undemocratic.
The treaty "clearly undermines Irish neutrality" and committed the country to the Common Foreign and Security Policy as well as the progressive framing of a common defence policy, he said.