Nortel Networks will shed 265 jobs across its operations in the Republic and Northern Ireland, with most redundancies coming from its Galway facility.
The Canadian telecoms giant said 115 jobs would o at its Monkstown plant on the outskirts of Belfast, where 1,250 people are employed, while 150 jobs will be lost at its Galway plant.
The latest redundancies are part of a global programme announced earlier this month by Nortel to shed a further 20,000 workers from its payroll.
It is also in the process of off-loading non-core businesses which employ 10,000 people.
The telecommunications group wants to reduce its overall workforce to 45,000 people as part of a drive to achieve a break-even cost structure.
News of the redundancies was broken to the 550 existing staff at Nortel's plant at Mervue in Galway at lunchtime yesterday. The entire systems house section of the Galway plant will be closed, and this work will be consolidated in Belfast, a company spokesman said. The Mervue operation has already shed 100 jobs over the past year.
Last December, Nortel Networks employed 100,000 people globally, but this has now been more than halved - to 45,000.
The company has sustained considerable losses, estimated at $15 billion (€16.5 billion) for the first quarter of this year and at $3.6 billion for the third quarter.
SIPTU's regional secretary for the west, Mr Joe Cunningham, said it was a terrible blow for the staff and, additionally, was serious in terms of the effect on regional development.
The Government must now pay more than "lip service" to regional development, and must make a commitment to Aer Lingus and Shannon, Mr Cunningham said. A "frightening number" of companies in the region had raised access difficulties with him in the past few months, and he was fearful of further cutbacks if action was not taken.
Nortel will be left with 400 on its payroll in Galway after these latest job cuts - almost half its original workforce at peak. The research and development facility will be expanded, a company spokesman said, emphasising that Galway had a product development centre which was recognised worldwide.
"This is an extremely difficult decision for us, and we'll be doing everything we can to minimise the impact," the spokesman said. There have already been consultations with SIPTU on a redundancy package.
Nortel had employed more than 700 people at its peak in Galway several years ago.
The latest redundancies in Belfast will be the fourth round of job cuts in the current financial year.
It is understood the redundancies will take effect across a number of departments and that up to 50 research and development jobs will go while a further 50 jobs will be axed in the systems department.
It is likely that 15 support function positions will also go at the Monkstown site.
Trade union leaders in the North said workers were particularly upset by the new redundancies because there had been high hopes the plant would escape Nortel's latest workforce reduction plan.
Nortel manufactures telecommunications transmission equipment including fibre optic equipment at its plant in Monkstown.
The plant is focused on the group's optical and metro internet businesses, two of Nortel's projected high-growth areas.
