Eir has announced the loss of 750 jobs after a majority stake takeover by two French firms connected to a telecoms billionaire.
The acquisition by Xavier Niel's companies is part of cost-cutting initiatives by Eir which has been underway for several months.
Staff were contacted this morning about the plans, with Eir saying that all redundancies will be entirely voluntary.
They will then have 30 days to consider whether to accept or decline the offer.
It has been reported that the cuts will not impact Eir's plan with the government to provide high-speed broadband to premises around the country.
It was first announced in December that Mr Niel's firms, NJJ and Iliad, would be buying 65% of Eir in a deal worth €650m.
Fears had been mounting in recent weeks that large job losses may be looming.
Eir currently employs more than 3,200 staff.