Workers in the National Ambulance Service (NAS), who are members of the Unite trade union, are to be balloted for industrial action in a dispute over outsourcing.
It follows a similar move by SIPTU which also represents NAS staff.
Unite has accused management of taking a unilateral decision to outsource inter-hospital ambulance transfers in the greater Dublin area to a private operator.
The union said that earlier this week it emerged that NAS management had initiated a tendering process without consulting the relevant unions.
"This follows recent proposals, rejected by unions, to reduce minimum paramedic crewing levels in emergency ambulances," Unite said.
The union added that the unilateral decision to outsource services to a private operator is in breach of the Public Service Agreement.
"Unite members will not tolerate any threat to patient safety or workers' terms and conditions in order to plug staffing gaps," said Unite General Secretary Sharon Graham.
On Friday, the Health Service Executive (HSE) said it was 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 HSE spokesperson said.
