Hundreds of engineering workers have been issued with redundancy notices across central Scotland.
Sources at Doosan Babcock said the firm was laying off staff on short-term contracts as projects at Grangemouth and the Levenseat waste management site draw to a close.
The GMB union said about 350 staff could be affected.
It was understood that Doosan Babcock’s core staff of approximately 800 is not affected by the redundancies.
Gary Smith, Scottish secretary of the GMB union, said: “This is a devastating start to the year for the workers and their families. It is a hammer blow for a Scottish economy that is already struggling.
“The news is also hugely damaging to the economic credibility of the Scottish government.
“These are transferable skills and Scottish yards and industries should be booming with construction work, fabrication for the renewables sector and North Sea decommissioning.”
Economy Secretary Keith Brown said the news was “deeply disappointing” and he would be seeking an urgent meeting with the company and the unions.
He added: “We will of course do everything we can for the workers.
“We know this will be an anxious time for the company’s employees, their families and communities in the surrounding area.
“We will provide support through our Partnership Action for Continuing Employment (Pace) to any employee who needs it.”