Nurses are to seek the opinion of the European Commission in pursuit of their pay claim but have warned that industrial action could be imminent.
The Irish Nurses' Organisation (INO) and the Psychiatric Nurses' Association (PNA) said it could not accept last week's report of the Public Service Benchmarking Body which awarded a pay rise to some senior nurses because the claim was outside its terms of reference.
In a joint statement, the unions said they would give the Labour Court "one last chance" to deal with their claim and Des Kanvangh general secretary of the PNA said the "nuclear option" of industrial action would also be considered.
Deputy general secretary of the INO Dave Hughes said the benchmarking decision was "incredible" considering the Labour Court and the National Implementation Body (NIB) had for five years refused to address nurses claims, saying they must be dealt with under benchmarking.
The NIB had recommended that benchmarking take into consideration the "expanded role for nurses", the adoption of new rosters and other proposed efficiencies.
Mr Hughes said: "What we are now left with is a Benchmarking Body which contradicts every one of those statements which has been made by the Labour Court and they have effectively rubbished what the National Implementation Body said.
He was also critical of the body's finding that it would not make an award if it found work of equal value was not being rewarded with equal pay. He said this contravened the EU directive on equal pay for men and women and he would be seeking the opinion of the European Commission's Advocate General.
Mr Hughes noted that the Labour Court had made a legally binding determination that the agreement governing nurses pay was indirectly discriminatory against women.
Both unions said they would be meeting with members over the coming weeks to discuss their options, which could include the unprecedented step of all-out strike.
"Dismay has turned rapidly to anger and over the coming weeks that anger must be reflected ... [the Labour Court] is the last chance motel," Mr Kavanagh said.
Nurses engaged in seven weeks of rolling stoppages which ended just before the general election last May when they agreed to leave their claim for a 10.6 per cent pay increase and pay parity with other grades of public servant to the Benchmarking Body.
Last week, the body said it could not deal with most of the claims of the 40,000 nurses and recommended pay rises for around 1,000 senior nurses. It also rejected a claim for a Dublin weighting allowance.
The unions said today that only the matters which had not been heard would be referred the Labour Court.
Sinn Féin spokesman for workers rights Arthur Morgan gave his support to the nurses. He said the "fatal flaw" of benchmarking had been exposed by the failure of those on lowest pay to benefit from the process.
He said this was due to the application of income disparities in the private sector being applied to the public sector.