A total of 370 jobs are to be lost at the Flextronics plant in Tullamore, Co Offaly, with the company moving the bulk of the operation to low-cost locations in Asia.
The factory, which manufactures casings for major computer companies, employs 440 people.
Flextronics director of operations Mr Michael Jennings said the company had made its decision to meet the needs of a major client.
"A significant proportion of our business which serves a particular customer is required to transfer to Flextronics in Asia, and China particularly, and in order for us to still keep that business and stay competitive and meet that particular customer's requirements, we're going to have to move that business to Asia," said Mr Jennings.
He described the decision as customer-driven. "At the end of the day, especially with the economic environment as it is, we don't want to lose business."
Mr Jennings said the decision was not due to lost contracts or declining orders. "Flextronics has not lost any contracts. The business is going to another Flextronics company, so I guess Tullamore has lost," he said.
Last October, the company said it was cutting 10,000 jobs worldwide, or 15 per cent of its workforce, as it announced a net loss for its third quarter of $329.8 million.
"As it turns out, this looks like an example of some of the things it will be necessary to do," said Mr Jennings. "Certainly, it is a terrible situation for all of us at Tullamore."
The closure is a further blow to Tullamore, which has already seen the closure of the Lowe Alpine and Snickers factories last year. Flextronics operates from a factory which was previously owned by the Atlantic Mills Clothing Company which closed three years ago.
The 70 remaining jobs at the Tullamore plant are involved in a different business, according to Mr Jennings.
"It's lower volume, higher complexity products and because of that it is less prone to fierce cost pressures of high-volume product which tends to go to lower cost regions," he said.
Last night, workers at the factory were angry with the manner in which the cuts had been announced, with some saying they had first heard the reports from news bulletins.
"That's very unfortunate and I told the workforce that's not how we would have wanted it and certainly Flextronics hadn't briefed the media before its own employees," said Mr Jennings.
Fine Gael employment spokesman Mr Charlie Flanagan called on the Tanaiste to visit Laois-Offaly and spearhead a job-replacement drive in the area, which he described as an economic black-spot.
The Tánaiste said the Government was determined to attract new industries to the region.
"I am confident that over the next few months there will be better news for the county, as a number of potential investors are currently in negotiations with the IDA with a view to locating in the area," she said.