Eircom is to seek 2,000 redundancies, a company spokeswoman has confirmed.
The lay-offs are expected to be completed by the middle of 2014. The redundancies will be across the company and is not yet known whether they will all be voluntary.
The company said the job cuts would bring eircom, which currently has 5,700 employees, in line with the European average for employee numbers and operational costs.
Eircom said in a statement that it had informed union representatives and planned to start discussions with them on the programme shortly.
Eircom chief executive Herb Hribar said the company faced considerable challenges.
“They require a fundamental transformation in the way we are organised, the business activities we prioritise and the work practices we have adopted in order to substantially reduce our costs and become more efficient,” he said.
Meanwhile, general secretary of the Communications Workers' Union Steve Fitzpatrick said the job losses would have to be negotiated by the company and its workers.
"I hope that we do not have to remind anyone that workers at eircom negotiated and agreed a very difficult rescue plan for the company which resulted in significant cost savings, and sacrifices by workers and their families, to support the company," he said.
"We welcome the management's commitment to engaging with the eircom workforce and their union representatives and we wish to stress that any further reductions in job numbers must follow established protocol and be on a voluntary basis only."
The cost-saving programme will include the consolidation of under-utilised office locations across Ireland, the company added.
The scale of lay-offs at the troubled telecoms provider, which owns the Meteor mobile network, is twice what was expected earlier this year.
During an examinership process in the Commercial Court, a rescue package was unveiled which at the time involved 1,000 job losses as part of a five-year restructuring plan.
Three businesses - eircom Ltd, Meteor Mobile Communications Limited and Irish Telecommunications Investments Limited - were affected by the examinership, which was reported to be the largest in Irish corporate history.
Under the business plan proposals before the court, eircom’s gross debts were to be reduced from about €4 billion to about €2.35 billion.
The company was valued at about €8.4 billion around the time of its high-profile flotation in 1999.
Additional reporting: PA