Workers at broadcaster and telecommunications company Virgin Media are being balloted for industrial action.
The move affects members of the Unite trade union.
It announced that members had unanimously decided to ballot for industrial action, up to and including strike action.
It follows an announcement earlier this month that the firm plans to cut up to 65 jobs.
Unite claims the decision was made to issue redundancy notices "without having consulted the unions involved" either before or after the announcement.
Unite and SIPTU had previously written to the company, reminding them of their obligation to engage in a 30-day information and consultation period before issuing notices of redundancy.
It says the company has failed to respond to the unions' letter to date.
Virgin Media previously said it was entering "a transformation and efficiency programme" to ensure continued revenue growth in a highly competitive market.
It says it has entered a 30-day consultation period with staff members.
But a company spokesperson adds: "Roles impacted do not fall under the collective bargaining groups therefore consultation with the unions was not required.
"Employee representatives have been nominated in the business. We are aware of and are adhering to our legal obligations."
Unite regional officer Brendan Byrne says: "Following the decision by Virgin Media to issue notices of redundancy without engaging collectively with the workers through their unions, Unite members held a general meeting at which they unanimously agreed to ballot for industrial action, up to and including strike action.
"It is our understanding that SIPTU will be adopting a similar approach.
"By failing to respect the mandatory 30-day consultation period, the company is in breach of its legal obligations.
"Our members have also been shocked to learn that the redundancy package being proposed by the company is inferior to that agreed with unions in 2015."
He adds: "No redundancies should be imposed before a full consultation process has been carried with a view to minimizing job losses, as required by law.
"Furthermore, any redundancy packages following this process must be in line with the agreement reached between unions and the company in 2015."
Unite is urging Communications Minister Richard Bruton to intervene.