HSE support workers at University Hospital Waterford are to be balloted for industrial action.
Trade union Unite said it is because of a HSE application to the High Court for an injunction against employees who have refused to pass picket lines.
More than 125 Unite members, working for cleaning services provider Momentum, have been on strike since Tuesday, February 25.
The dispute centres on union claims that conditions of employment had been changed since the company took over the provision of cleaning services at the hospital.
Unite Regional Officer Tony Kelly said: “Rather than instructing Momentum to abide by accepted industrial relations procedures and desist from imposing unilateral changes to our members’ conditions, the HSE decided to aggravate the situation by seeking an injunction against Unite members working for the HSE who refused to pass pickets placed by their Momentum colleagues.
“Following this provocation, a general meeting of Unite members working for the HSE decided to ballot for industrial action unless the HSE withdraw its application to the High Court and immediately instructs Momentum to reverse the unilateral changes to our members’ working conditions.
“Resolution of this dispute is in the HSE’s hands.”