Members of SIPTU in the National Ambulance Service (NAS) are to be balloted for industrial action, up to and including strike action.
The union has accused management of attempting to outsource inter-hospital transfers in the greater Dublin area to the private sector.
According to SIPTU, a decision has been made to undertake a tendering process to outsource transfers without consultation, engagement or sharing of information with the trade unions representing NAS staff.
The union said that inter-hospital transfers are carried out by Emergency Medical Technicians working in the NAS Intermediate Care Service.
"SIPTU members fear that other such processes will now take place to outsource this work in other parts of the country," said SIPTU Sector Organiser, John McCamley.
"This attempt to outsource our members' roles is a blatant breach of the Public Service Agreement protocols on outsourcing and on procedures around consultation and engagement."
"It has left our members with no other option but to ballot for industrial action up to and including strike action," Mr McCamley said.
SIPTU represents around 2,000 ambulance personnel working as EMTs, paramedics, advanced paramedics, ambulance supervisors, ambulance officers and control centre staff.
The HSE said it is not aware of any action or intention to outsource inter-hospital transfers and remains committed to the staffing of its Intermediate Care Service through the National Ambulance Service.
"The HSE understand that SIPTU has escalated the matter to the Health Sector Public Service Agreement Forum, which is the agreed dispute resolution mechanism under the Public Service Agreement for matters such as this, and a meeting of the forum is proposed for next week," a spokesperson said.
