A nurses' strike could be on the cards.
Delegates at a special conference of the Irish Nurses and Midwives' Organisation (INMO) have voted by 92% to reject the government's latest pay proposals.
The union says the offer would have no impact on the majority of nurses and midwives.
It is now expected that INMO members will be balloted next month on the pay offer.
If rejected, a second ballot for strike action will follow.
"The message from today’s conference was clear. Nurses and midwives are deeply frustrated with our health service," said INMO General Secretary Phil Ní Sheaghdha.
"The government’s proposals are simply not going to make a dent in the number of vacancies across Ireland. We are calling for members of political parties to stand with us to secure the future of our health service.
"Without a pay rise across the board, our health service will not be able to recruit and retain the nurses and midwives Ireland needs. That means more overcrowding and pressure on staff, with patients suffering as a result.
"As ever, we remain open to further discussion with the government.”