A wage freeze in the public sector may push nurses to vote in favour of industrial action.
The Government's calling it a pay restraint, which will now be reviewed six months earlier than forecast.
Public hospital nurses are already in pay talks and voting on whether to strike, with results expected on Friday.
Nurses Organisation industrial services manager Glenda Alexander says it's completely unacceptable to change the rules in the middle of negotiations.
"[Nurses] have already reached an impasse over those negotiations. They're not happy people at the moment, our members, they are pretty let down and upset."
She says they are halfway through pay negotiations with public nurses.
"This was sort of just dropped on ys."
Nurses are already voting about whether to strike over their collective contract, with results expected on Friday.
LISTEN ABOVE