Up to 350 manufacturing workers at risk of redundancy
Doosan Babcock informed unions of the plans, which affect sites in Grangemouth and Lanarkshire.
Unions have been told 350 Doosan Babcock manufacturing jobs in central Scotland are at risk of redundancy.
The GMB said up to 300 manual and 50 managerial posts at Grangemouth and the Levenseat waste management site in Lanark could be affected.
It is understood the dismissals, which have been proposed following the completion of contract work, could take effect between February and May.
Doosan Babcock, which is based in Renfrew, currently employ more than 800 people.
Unite have also been notified about the plans.
Gary Cook, GMB regional organiser for engineering and construction workers, said : "This will be yet another devastating blow for skilled workers in Scotland.
"We are seeing massive job losses throughout Scotland in engineering and construction sites with thousands more likely to lose their jobs at Rosyth following the completion of the aircraft carrier projects."
Mr Cook said opportunities are traditionally created elsewhere in the sector when work dries up.
But he claimed the union has evidence UK workers are being "locked out" of applying for jobs at energy to waste plants currently under construction by foreign companies.
Scottish Labour leader Richard Leonard expressed concern about the proposed cuts.
Mr Leonard said: "The Scottish Government needs to intervene immediately to support all those highly-skilled people facing redundancy, and work with the trades unions involved to avert these job cuts.
"Scotland's economy cannot afford to lose these skilled workers jobs."
He also claimed the SNP have "no industrial strategy".
Mr Leonard added: "It does not use its powers of procurement to support jobs and Scottish supply chains.
"We need direct action to stimulate the construction sector and tougher action to ensure that the highest standards are met on contracts like these."
Economy Secretary Keith Brown said: "The news of job losses at Doosan Babcock is deeply disappointing, and I will be seeking an urgent meeting with the company and the unions to establish the full facts.
"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."