The clothing company, Hawkesbay, is to close its plant in Ardee, Co Louth, with the loss of 300 jobs.
A further 160 workers will be made redundant at its plants in Derry and Newtownards, Co Down, it was announced yesterday.
The lay-offs are the result of the loss of the company's main contract. Staff at the plant in Ardee were told by management yesterday of the closure planned for February 4th.
In a statement, the company said the closure and lay-offs were necessary because its main source of work, V.F. Corporation, the makers of Lee and Wrangler jeans, will not renew the existing contract, which expires at the end of the month.
Yesterday, SIPTU, the union representing the workers wrote to the Tanaiste, Ms Harney, and spoke to Department of Enterprise, Trade and Employment officials requesting an urgent meeting.
Mr George Hunter, SIPTU's northern counties regional secretary, said: "This came as a bolt out of the blue to us. I've written a letter to the Tanaiste seeking an urgent meeting to try to see if there is anything that can be done to reverse the decision to close the plant."
At least, he said, they wanted a postponement of the decision to close.
There are 300 workers at Ardee, which will close; 250 in Derry, where there will be 70 redundancies; and 150 in Newtownards, where there will be 90 redundancies.
The two Irish companies, Hawkesbay Apparel Ltd and Hawkesbay Sportswear (Ireland) Ltd, are owned by Hawkesbay Sportswear Inc, based in Nassau, Bahamas.
Hawkesbay Sportswear Inc bought the Irish operations on February 1st 1998 from V.F. Corporation, which manufactures the jeans, and which has provided the company's main source of work.
In the statement, Hawkesbay said: "Despite lengthy negotiations and considerable price reductions, Hawkesbay has not been successful in persuading V.F. Corporation to renew the contract which is due to expire on January 30th, 2000. "The V.F. business has been adversely affected in the UK and elsewhere in Europe and last year they closed their factory in Scotland."
The plant in Ardee had been overly reliant on the V.F. contract. The company said it was confident about continuing its operations in Derry and Newtownards, albeit with redundancies, because rather than being overly reliant on contract work, it had launched its own brand last September and intended to expand sales in the UK and the US.
Hawkesbay said it was tying down new contracts with high street retailers and other branded companies in the UK, Germany, Scandinavia, and the US. Senator Fergus O'Dowd (FG) said the closure would have a devastating effect on the local economy.