The Psychiatric Nurses Association has warned that it may stage more ambulance strikes if the Health Service Executive does not engage on its right to represent members.
A ten-hour strike by around 500 ambulance personnel took place earlier today.
The dispute centres on the HSE's refusal to recognise the PNA and its ambulance personnel's branch NASRA as representatives of the staff in question.
PNA members in the National Ambulance Service (NAS) mounted pickets between 7am and 5pm around the country in pursuit of their right to be represented by the union of their choice.
The HSE said that recognising yet another union would impair good industrial relations within the NAS.
It has also refused to deduct union subscriptions through the payroll system as it does for other unions.
The PNA only represents 500 of the National Ambulance Service's 1,800 staff; most of the remainder belong to SIPTU.
The PNA provide contingency cover for life-threatening, potentially life-threatening and humanitarian cases.
The HSE said it had managed the situation, despite the challenges it experienced.
Contingency arrangements included the deployment of Department of Defence army ambulances and managers who are qualified paramedics are also carrying out frontline duties.
Ambulance personnel picketing #Cork @HSELive Ambulance HQ - #PNA #Nasra represents 70 of the 150 ambulance personnel in county #strike @rtenews Pickets in #Dunmanway, #Castletownbere, #Midleton & #Macroom too. pic.twitter.com/JBaVlRu8mL— JennïeØSullivân (@OSullivanJennie) January 22, 2019
There were no delays to ambulance services around the country despite the strike, according to the director of the NAS.
Speaking on RTÉ's News at One, Martin Dunne said that as of midday the service had received approximately 265 calls and had attended to all calls.
He added that army ambulances had been dispatched as part of the contingency plan involving the Department of Defence.
Mr Dunne said the situation had "been challenging" but was monitored closely.
SIPTU said it had no indications at this time that its members refused to pass PNA paramedic pickets.
It noted that the PNA had not asked other unions to participate in the strike.
Additional reporting Jennie O'Sullivan