Nurses in Northern Ireland are to vote on potential industrial action amid an on-going pay dispute with Stormont.
The Royal College of Nursing (RCN) said the ballot of its members represented an "unprecedented move".
Nurses will be asked to vote on action that stops short of an outright strike - rather a work-to-rule form of protest, with steps such as a refusal to work unpaid hours.
The RCN has accused Stormont's Health Department of failing to make a pay award for 2015/16.
It said Northern Ireland was now the only part of the UK in which nursing staff have not received any pay rise, claiming local nurses are at least 10% worse off, in real terms, than in 2008.
Janice Smyth, director of the RCN in Northern Ireland, said: "The failure to give a pay award to nurses in Northern Ireland is a failure in equality. Not only are our members now paid less than their counterparts in England, Scotland and Wales, but many other public servants in Northern Ireland have received a pay award, leaving nursing, a predominantly female profession, subjected to unfair treatment.
"An experienced staff nurse in Northern Ireland is now paid £279 a year less than in England and £561 a year less than in Scotland. The message that the care they provide to the people of Northern Ireland is not valued is being made loud and clear.
"Nurses and Health Care Assistants are committed and dedicated to the care of patients. This is borne out in practice when, as a result of trying to provide nursing care in a system that is not fit for purpose, they often take on additional roles to ensure the effective delivery of services. This has resulted in enormous pressure on the nursing workforce.
"The decision to ballot our members was not taken lightly. When we end up in a situation where there appears to be no alternative to industrial action, then we know that nursing staff have been pushed to the limit.
"The RCN has made efforts to engage in discussions about pay but unfortunately it would appear that nurses' pay is not considered a priority for the DHSSPS (Department of Health, Social Services and Public Safety)."
A spokesman for Northern Ireland's Health Minister Simon Hamilton said: "The minister values the essential role that nurses play in the continued provision of a high standard of care in Northern Ireland. His priority is the delivery of high-quality, safe and effective services for patients and clients.
"The minister is aware of the RCN council decision to ballot their members in NI for industrial action and has indicated his disappointment that this is the case.
"His department is keen to progress discussions with HSC trade unions. Officials have repeatedly sought to engage with trade unions who have refused to enter into discussions on a settlement for 2015/16. The department remains hopeful this will change and that unions will engage."