Campaigner Mr Denis Riordan and former High Court judge Mr Rory O'Hanlon are among a group who will today announce a new campaign against the Nice Treaty.
The No To Nice Campaign intends to oppose the treaty in order to prompt "a radical reassessment of our role in the European Union".
It will formally begin in Dublin this afternoon.
The chairman of the group is Mr Riordan, who last year made a legal challenge to the proposed appointment of Mr Hugh O'Flaherty as vice-president of the European Investment Bank.
In a statement yesterday the organisation said the EU was becoming much more than an organisation to promote European co-operation. "It seems the EU is seeking to become a federal superstate which will make use of an all powerful bureaucratic apparatus to bully and indeed bury the European nation state," it said.
The campaign also opposes "the final abandonment of Ireland's neutrality inherent in the Irish Army taking part in the Rapid Reaction Force - the core of a future European army".
The statement said the concept of "enhanced co-operation" as outlined in the treaty was "a code word for using its institutions to create a second class status for smaller states like Ireland".
Meanwhile, the Minister for Foreign Affairs, Mr Cowen, has rejected Sinn Fein's contention that EU membership had contributed to the demise of Irish agriculture.
"This extraordinary statement will no doubt come as a surprise to the leaders of the IFA and ICMSA, as well as many farming families and those involved in the hugely successful agri-business sector," he said.
"Mr [Gerry] Adams is clearly unaware that Ireland has received £24 billion from the Common Agricultural Policy since we joined the Union."