Vacuum cleaner manufacturer Hoover Candy is to close its Cambuslang factory with the loss of 260 jobs.
The plant dates back almost 60 years
The production carried out at the plant near Glasgow will be moved to factories in Wales and China.
A company spokeswoman said about 70 jobs could be created in Merthyr Tydfil, but did not know if they would be new posts or filled by workers transferred from Glasgow.
The company plans to retain a further 90 engineering and sales positions in Scotland, but will move them to other premises.
The engineering union Amicus said the closure was a "terrible blow" for employees and the community and promised to fight the closure.
Scottish regional secretary John Quigley estimated that up to 1,000 jobs could be lost at firms which supplied Hoover.
'Stunned and angry'
"Amicus and the Scottish Executive will be seeking urgent meetings with the company to look at avenues to save jobs and turn round this bitter pill of an announcement," he said.
Senior shop steward Eddie McAvoy read out a statement on behalf of the workers, who said they were "stunned and angry" at the announcement.
The statement said the workforce was being thrown on the dole after giving the company 100% support.
"As far as the shop stewards are concerned, we will be recommending rejection of the company's statement and will be contacting our full-time officials, MPs and MSPs to start a campaign to save Cambuslang," it said.
Hoover said it "regretted" the move and paid tribute to its workers.
Peter Murtagh, the division's vice president, said: "This is undoubtedly a very difficult time for all employees.
"With continued investment from our parent company, and by working with all our employees, we had hoped this situation would not arrive.
"However, despite all these efforts and hard work we have been unable to reduce our manufacturing costs sufficiently.
"With the selling price of vacuum cleaners continuing to decline throughout our European market, regrettably these radical steps have to be considered for the company to continue."
A 90-day consultation period with employees and unions has been launched.
Mr Murtagh confirmed that Hoover wanted to retain its design and development engineering function and its service operation in the area.
However, he said it would have to look for other premises as the existing plant was too large.
Hoover has been manufacturing vacuums in Cambuslang for almost 60 years, employing 5,000 people during the 1970s.
Last year the company said a contract to build a new generation of cleaners would safeguard jobs at Cambuslang.
It had fought off competition from a sister plant in Portugal to clinch the £1.25m deal.
That work is now expected to be moved to the plant at Merthyr Tydfil in Wales by early 2004.
Hoover Candy spokeswoman Caroline Knight said the move would strengthen the Welsh site's prospects but could not guarantee its future was safe.
She said: "The domestic appliance market is a rapidly changing market. It's a very difficult situation. There's no predicting what will happen in the future."
BBC Scotland business correspondent Hayley Millar said the Cambuslang factory had been losing about £1m a month despite "substantial" investment.
Minister for Enterprise Jim Wallace said he was "extremely disappointed" at the proposal to cease manufacturing at Cambuslang.
Mr Wallace said an action team designed specifically to help those facing
redundancies train for new and updated skills was ready to help out if
"Our main concern would be to ensure that everything possible is done to
assist them to find alternative employment," he added.
Scottish National Party economy spokesman Jim Mather called for drastic change to prevent similar decisions being taken by other companies.
Mr Mather said: "It's all well and good for the government to offer grants to attract business to Scotland, but we need the powers and other incentives to help keep these companies and the full range of jobs they provide."