British Telecom (BT) is to cut 13,000 jobs over the next three years as part of a restructuring plan to invest in ultrafast broadband and the next generation of mobile communications.
It is not known where the job cuts will be.
The company employs more than 600 people across five cities as part of its Irish operations.
They are also the current organisers of the the annual BT Young Scientist & Technology Exhibition.
Britain's biggest telecoms operator, which announced 4,000 job cuts a year ago, said middle management and back office roles would face the brunt of the cull.
The company also said it would hire about 6,000 front line engineers, customer service and cybersecurity experts.
BT chief executive Gavin Patterson is under pressure from investors to improve the company's stock performance, which has almost halved over the last two years.
The company has been reeling from an accounting scandal in Italy last year, and has spent billions on buying football rights to attract customers to it pay TV channels.
It also spent stg£12.5bn (€14.2bn) to buy British mobile phone operator EE in 2016.
The FTSE 100 company said the jobs cuts would enable it to cut costs by stg£1.5bn (€1.7bn).
"This plan will help BT become a leader in converged communications; continue to power the UK's digital economy; and drive greater value for shareholders," the company said in a statement.
One-third of the job losses will take place overseas.
Its headquarters near the London Stock Exchange will be closed, although it will still maintain a smaller presence in London at a yet to be decided location.
In a statement to Newstalk.com, BT Ireland said: "There are no details at this stage of either the reduction in roles, or the new jobs, we have announced today.
"We have been clear, however, that the changes will represent an investment in the jobs and skills needed to strengthen our networks and customer service."
The company has operations in 180 countries.
Additional reporting: Jack Quann