The Royal College of Nursing (RCN) has announced it will take a ballot of members to consult on whether to strike in Wales over pay.
The move follows a decision by the Welsh Government to award nurses a 3% pay increase in July.
The increase followed a recommendation of the independent pay review body, but while it has been backdated to April, unions say 3% is an “effective cut in real terms pay”.
In a previous ballot, 94% of RCN Wales members who voted stated the pay rise was unacceptable.
The union believes industrial action is a last resort, but argues that an NHS staffing crisis in Wales is causing an unacceptable risk to patient safety.
RCN Wales board chair Richard Jones said: “The anger and frustration of our members is clear. Nursing staff deserve a fair pay rise.
“The 3% pay rise proposed by the Welsh government is below projected inflation and living costs in Wales and the RCN believes it is nothing short of an insult.
“Just as it’s our responsibility as a Royal College to defend patient safety, it’s our responsibility as a trade union to fight for our members.”
Helen Whyley, director of the college in Wales, said: “Our members are angry that the Welsh Government will not discuss an increase in the NHS pay award.
“Nursing staff are critical to safe patient care and have shown their outstanding commitment to serving the public over the challenging times of the last 18 months.
“With over 1700 nurse vacancies in Wales there are insufficient numbers of nursing staff to care for patients safely and effectively. Our members are feeling undervalued, disenfranchised, and angry.
“If the Welsh Government are serious about ensuring safe patient care, they must prioritise nursing by increasing this pay award to keep nurses working in the NHS in Wales and make it a more attractive career.
Earlier this month, the first minister defended his government’s decision.
In response to Thursday’s announcement, a spokesperson for the Welsh Government said: “We hope NHS workers understand how much we value their work and appreciate everything they have done.
“We have accepted the independent pay review body’s recommendations in full.
“While it is disappointing the RCN is proceeding to a ballot, we have developed a package of enhancements within the funding available which focuses on supporting our lowest paid staff.
“While we want to invest in our workforce we also need to invest in delivering vital NHS services.”
The ballot will open on November 4 and will ask members whether they are willing to take industrial action.