Two of the State's biggest unions have clashed over the merits of the proposed new partnership deal, with one claiming it is "not worth the paper it is written on".
Mandate, which represents thousands of low-paid workers in the retail sector, said workers had been "sold a pup" by those who had negotiated the agreement, Towards 2016.
Recent energy price and interest rate increases meant the pay element of the new deal was already "practically obsolete", the union added.
In a strongly-worded response, Impact, the State's largest public sector union, said those who were seeking a rejection of Towards 2016 were "playing a dangerous game with workers' living standards".
Unions are currently balloting members on the agreement, which provides for a 10 per cent pay increase over 27 months.
A decision on whether to formally ratify it will be taken at a special conference of the Irish Congress of Trade Unions (Ictu) on September 5th.
Although Mandate is affiliated to Ictu, it declined to take part in the negotiations on the deal, claiming social partnership had failed to address the issue of low pay. The union has instead served separate pay claims on major retailers.
Mandate national official Linda Tanham said the 0.25 per cent increase in interest rates announced last week by the European Central Bank brought into focus the "failure at the heart" of the new agreement.
"The interest rate jump, combined with recently announced increases in utility bills such as ESB and gas, has rendered the minimal pay increases negotiated at the recent pay talks practically obsolete before the ballot on Towards 2016 has even been concluded," she said.
Ms Tanham said that with inflation running at almost 4 per cent, it was clear that the position taken by Mandate in relation to the negotiations had been vindicated.
"It now appears that we have been sold a pup and the nominal pay increases provided for under the Towards 2016 are not worth the paper they are written on for thousands of working families."
She added: "In effect, the interest rate hike represents more than many workers will receive under the recently concluded agreement. Moreover, additional increases are expected over the coming months."
Impact spokesman Bernard Harbor said higher pay increases would not be available if the new agreement was rejected.
"Towards 2016 will deliver pay rises of over 10 per cent in 27 months, plus the best package of workplace rights available anywhere in the world. The critics say this isn't good enough, but none of them have a concrete alternative," he said.
Mr Harbor said that in seven months of talks, employers had resisted "every extra cent on pay and every plank of the employment rights package".
It was, therefore, "nonsense", to suggest that the Government or employers would give more than what had already been conceded if the agreement was not accepted.
He added that Ictu negotiators had taken account of likely interest rate increases and higher gas and electricity bills during the negotiations.
"No one has a crystal ball and many of the factors that cause inflation are out of our control, but Ictu's inflation projections have been the most accurate - and the most pessimistic - of anyone's in recent years, and they suggest that the deal will beat inflation.
"It's frankly unreal to say that increases of over 10 per cent are worthless to low paid workers."
Impact general secretary Peter McLoone was one of the key negotiators of the agreement in his role as current Ictu president.
