Nurses in the intensive care unit in University Hospital Limerick will begin industrial action in the form of work-to-rule this morning.
The Irish Nurses and Midwives Organisation (INMO) said the "unprecedented step" is over staffing at the hospital.
The INMO said the ICU is currently operating at a 22 per cent staffing deficit, with all ICU beds still open to admissions.
INMO assistant director of industrial relations Mary Fogarty said: "Regularly shifts in the ICU are significantly depleted and this is predicted to continue. Our members are very concerned about the potential deviation away from one nurse to one patient care in the ICU.
"The lack of consistent safe staffing in the intensive care unit is having a detrimental impact on the physical and mental wellbeing of our members working in this unit and their patients."
The INMO said it had engaged extensively with hospital management and the Workplace Relations Commission (WRC).
Ms Fogarty added: “In order to make staffing safe in UHL ICU and ensure that patients are getting the one-to-one care that is expected in an intensive care unit, the INMO is calling on hospital management to temporarily close two beds in the ICU pending the recruitment of suitably qualified and experienced ICU nurses. Unlike other hospitals experiencing similar nursing deficits, management in Limerick have been unwilling to do this thus far.
“Our members in UHL ICU have been working at full tilt since the beginning of the pandemic with very little reprieve. It is unacceptable that they are constantly expected to deliver nursing care in an unsafe care."
Ms Fogarty said the decision to begin work-to-rule industrial action had not been taken lightly, however, she said members "feel like all other avenues to resolve the issues that exist in UHL ICU have been closed off by hospital management".