Top-ranking civil servants have rejected the proposed Croke Park II round of pay cuts.
The Association of Higher Civil and Public Servants (AHCPS) overwhelmingly voted against the agreement, with 85% refusing to give their backing.
It is the fourth union to come out against the deal.
Members of the AHCPS are in line for cuts to wages as they earn more than €65,000 a year.
They are also due for changes to rosters, with the working week made longer, cuts to premium rates and some salary increments being frozen.
The union is supported by the Irish Nurses and Midwives Organisation, the Irish Medical Organisation, the Civil and Public Services Union (CPSU) and Unite in their opposition to the deal. Some 86% of AHCPS members voted in the ballot.
The Teachers’ Union of Ireland, the Medical Laboratory Scientists Association and the Technical Engineering and Electrical Union have already rejected the deal.
Other major unions such as Impact and the Irish National Teachers’ Organisation could hold the key to success or failure of Croke Park II.