The public sector union Impact has condemned Sinn Féin's rejection of the new social partnership deal, Towards 2016.
Sinn Féin's Arthur Morgan said the deal, which has yet to be ratified by union members, was "a spectacular failure for low-paid workers" and that the pay rises "barely keep pace with inflation".
Earlier today, the Louth TD called for the rejection of Towards 2016, which is being voted on by union members across the State over the next month.
But Impact general secretary Peter McLoone said the deal included the "best package of workplace rights available anywhere in the world".
The agreement includes a 10 per cent pay rise phased over 27 months, with an extra half per cent for the lower paid. "The critics say this isn't good enough, but none of them have said how they would better the deal," Mr McLoone said.
"In seven months of talks employers resisted every extra cent on pay and every plank of the employment rights package. So it's nonsense to suggest that Government and employers will give more if this is rejected."
Speaking after the party's ardchomhairle voted to call for the deal to be rejected, Mr Morgan outlined seven areas that he said were unacceptable. Mr Morgan said the deal was bad for public sector workers, 54,000 of whom are Impact members.
"The deal opens up the public sector to outsourcing with unions only having a right of notification. This will undermine the terms and conditions of public sector workers and could see them being replaced with non-union labour," Mr Morgan said.
Provisions for modernisation in the sector effectively meant workers were "obliged to give a blank cheque for their terms and conditions in order to secure wage increases". It also fails to act a check on Government privatisation plans, he said.
Ictu, which negotiated the deal with employers' body, Ibec, failed to secure a provision allowing for local bargaining to force prosperous companies paying more than agreed wage rises.
The State's largest union, Siptu, is voting on the deal and is expected to endorse it after strong support was expressed at a special delegate conference last month.
But around the same time, a number of Siptu officials joined with officials from other unions - including the ATGWU, the Irish Nurses' Organisation and Association Secondary Teachers of Ireland - in calling for a rejection of the deal.
The deal was worked out after a long talks process complicated by controversy over the treatment of foreign workers, particularly at construction firm Gama, and the Irish Ferries plan to replace Irish labour with cheaper foreign workers.