Eir has confirmed it's to cut 750 jobs.
In a statement, the telecoms firm said employees will leave as part of a voluntary redundancy scheme.
It also stressed that the job losses will not impact on the roll-out of broadband in rural areas.
The company said: "This has been launched in an effort to deliver costs savings and create a leaner, more agile organisation. In parallel, the company plans to simplify its products and business processes.
"Eligible staff have already or will shortly receive correspondence with a personalised financial estimate for their consideration.
"The terms of the scheme are aligned with previous similar schemes. A large percentage of the company’s field force is not eligible. The Minister and union representatives are being informed."
The trade union Fórsa said it is seeking "immediate engagement" with senior management.
While Steve Fitzpatrick, general-secretary of the Communications Workers' Union (CMU) said: "We have been informed by Eir that the company intends introducing a voluntary exit scheme seeking to reduce worker numbers by 750.
"We have no indication that this will be anything other than voluntary.
"We will engage with the company on the detail and, in particular, to ensure that proper arrangements are put in place to cover work once the scheme takes effect."
