More than 600 SIPTU members in RTÉ are to be asked to vote in a protective ballot indicating their intent to take industrial action, up to and including strike action, if the broadcaster attempts to further outsource any of the station's core programme productions or other roles.
In February, SIPTU members in RTÉ voted no confidence in RTÉ's New Direction Strategy, which the union said would result in the endless outsourcing of jobs and deal a fatal blow to public service broadcasting.
"The upcoming protective ballot will provide a clear indication of action that SIPTU members are willing to take to safeguard employment and the future of public service broadcasting in Ireland," said SIPTU Services Divisional Organiser Adrian Kane.
"SIPTU believes in a healthy mix of public and for-profit broadcast production, which complement each other rather than being presented as an either-or approach," Mr Kane said.
Last month, members of the National Union of Journalists (NUJ) in RTÉ also voted no confidence in RTÉ's New Direction Strategy.
The result of the NUJ ballot showed members voted no confidence by a margin of 89% on a 35% turnout.
RTÉ has previously said it believes that the five-year strategy, now in its second year of implementation, offers the best way forward to secure the future of Ireland's national public service media and give more to Irish audiences in a much changed media landscape and with rapidly evolving audience habits.
"This strategy was published following extensive consultation with the public, RTÉ staff and a wider group of stakeholders," an RTÉ spokesperson said.
"The vast majority of staff supported the need for RTÉ to evolve as outlined in the strategy during this consultation process.
"We continue to remain available to meet with the unions, as we have done, to progress these and other relevant issues," they added.