Thirty-eight hospitals and health care facilities face serious industrial disruption later this month as up to 10,000 health support staff have served notice of a 24-hour strike on Thursday 20 June.
In the letter notifying the Health Service Executive of the strike action, SIPTU also warns that if the HSE and related agencies refuse to enter meaningful negotiations, further 24-hour stoppages will take place on 25 and 26 June and on 2, 3 and 4 July.
Further strike action has not been ruled out.
The dispute centres on a job evaluation scheme for the grades in question, which the Government agreed to carry out during negotiations on the last Public Service Stability Agreement (PSSA).
The job evaluations examine whether the roles have changed and whether pay rises are warranted.
The Department of Public Expenditure and Reform said the matter of the job evaluation scheme dispute has been referred to the PSSA Oversight Group in line with the terms of the PSSA, which SIPTU has signed up to.
The union said the job evaluation scheme confirmed that pay rises worth up to €3,000 per year were justified, and accused the Government of reneging on implementing those increases.
Affected grades include health care assistants, maternity care assistants, laboratory aides, chefs, and surgical instrument technicians, as well as workers in portering, household and catering services.
SIPTU Deputy General Secretary for the Public Sector John King said members had accepted the provisions of all public service agreements since 2010, and the Government side must now honour its obligations under those agreements.
He said it was unacceptable that workers should be forced to go into an official dispute to get what they are owed.
He called on Minister for Health Simon Harris and Minister for Finance Paschal Donohoe to step in to avoid this dispute, which he said would undoubtedly bring pressures on the delivery of health services.
He said the union remained available for talks but that any such engagement must be about the practical implementation of those outstanding awards.
SIPTU Health Division Organiser Paul Bell said the ball was now in the Government's court and Minister Donohoe had a small three-week window to resolve the dispute or "face the consequences".
He noted that members had supported strike action by 95% and would not back down until they won their campaign for pay justice.
The HSE said it was disappointed that SIPTU had taken a decision to take strike action, which it described as unnecessary and would lead to "unnecessary disruption to the delivery of patient and client services if it goes ahead".
In a statement, the HSE said it would consider any contingency planning required to ensure there was no interruption to health care provision for service users.
It called on SIPTU "to avail of the dispute resolution mechanisms contained in the Public Service Stability Agreement to have its grievances considered, and requests that the union return to talks on all issues involved".
The strike action will take place at the following facilities and hospitals:
Cork University Hospital
Cork University Maternity Hospital
Kerry University Hospital
Mallow General Hospital
South Infirmary Hospital Cork
South Tipperary General Hospital
Wexford General Hospital
St Lukes Hospital Carlow/Kilkenny
Mercy Hospital Cork
Connolly Hospital Blanchardstown
National Rehabilitation Hospital
St Ita's Portrane
St James Hospital
St Vincent's University Hospital
Our Lady's Hospital Navan
Louth County Hospital
Our Lady of Lourdes Hospital Drogheda
Our Lady's Children's Hospital Crumlin
Central Mental Hospital
Midland Regional Hospital Mullingar
Midland Regional Hospital Tullamore
Midland Regional Hospital Portlaoise
Naas General Hospital
Cavan General Hospital
Letterkenny University Hospital
Sligo University Hospital
Roscommon University Hospital
Portiuncula Hospital Ballinasloe
Galway University Hospital
Mayo University Hospital
UL Hospital Dooradoyle
UL Maternity Hospital
UL Orthopedic Hospital Croom