Desmond and Sons, the clothing manufacturer, announced yesterday the closure of three of its factories in Swatragh, Co Derry, Omagh, Co Tyrone, and Irvinestown, Co Fermanagh, with the loss of 482 jobs.
The announcement follows the closure of two of the company's other plants in Derry and Dungiven last January with the loss of 315 jobs.
Yesterday's announcement means that Desmond and Sons, which just two years ago was Northern Ireland's biggest private-sector employer with a workforce of just under 2,500, now employs 800.
In January the company had six factories; now it has just one, at Newbuildings on the outskirts of Derry where 350 people make specialised jeans.
The company's remaining staff are employed at its headquarters in Drumahoe outside Derry and at the company's design centre in London, which between them have a staff of 450.
The Omagh and Irvinestown factories, which employ 229 and 115 people respectively, both make jeans, sweat shirts and track-suits. The Swatragh plant makes women's clothes and pyjamas.
Mr Alan Elliott of the GMB union said yesterday's announcement came without prior warning.
"I was invited to attend a meeting in Desmonds' headquarters in Drumahoe to discuss job evaluation.
"Just before the meeting started the company's director of human resources said she had an announcement to make. With that, two other directors walked into the room.
"I was chilled to the bone, not knowing what to expect. I knew there were possibly concerns about the factories at Irvinestown and Swatragh, but the fact that Omagh is to go as well came as a total shock. I was completely unprepared for the announcement, as indeed were the 482 people who are to lose their jobs.
"They are utterly devastated by this announcement, as I am. We're talking about 800 jobs down the tubes in one company since the start of the year, and it follows last week's announcement that 158 jobs are to go in a linen spinning mill in Sion Mills, Co Tyrone," said Mr Elliott.
Desmonds said in a statement that it recognised the announcement would come as a shock to it employees.
"Consumer demand for clothes at value-for-money prices and pressures on margins, coupled with increased insurance, energy and social costs mean that it is no longer possible to sustain large-scale manufacturing operations in this country. Our competitors have long since ceased to do so," the statement said.
"In order to compete for future orders, the vast bulk of production will have to be fulfilled in our overseas factories. "This has painful consequences in Northern Ireland."