The Green Party and Sinn Féin led the opposition to the the Government's proposed amendment and promised to campaign strongly against what the Greens' foreign affairs spokesman called "this cynical move".
Mr John Gormley added that the Nice referendum was being rerun without major adjustment and said this was evidence "of the democratic deficit in Europe".
He reiterated the Greens' claim that the Seville declarations were insignificant.
"We are hopeful that the Irish people will see through this scam. The declarations simply confirm a definition of neutrality which is so narrow as to be meaningless.
"The Irish declaration will mean that we continue as members of the EU Rapid Reaction Force and the Partnership for Peace. It will mean that military personnel and military planes can continue to land at Shannon without reference to the Dáil and that military manoeuvres can take place off the Kerry coast. All of this and the fact that they have refused to insert even a watered-down reference to neutrality in the Constitution exposes the Government's claims as bogus."
Sinn Féin said the fundamental issue in the campaign would be democracy itself, because the Government "defied the decision of the people in last year's referendum and encouraged the other states to ratify, assuring that the Irish would 'get it right' the second time".
The party's European affairs spokesman, Mr Aengus Ó Snodaigh, added: "If Germany or France or Britain had rejected Nice it would have been dead in the water. This proves the point that the Nice Treaty establishes a two-tier EU dominated by the larger states."
Also promising to campaign for a No vote, Mr Joe Higgins of the Socialist Party said the proposed opt-out clause on a common defence policy did not address objections to the "relentless drive toward the creation of a military wing for the EU . . . The Socialist Party will work vigorously for its rejection and will campaign instead for a democratic and socialist Europe where power is in the hands of the ordinary people."
