Jobs look set to go at the BiFab marine engineering yard in Burntisland, Fife, with the site possibly closing by the end of June.
Union officials have been told by managers at the yard that redundancy notices will be given to the core workforce today.
The Fife site has been targeted along with a yard in Lewis.
The Unite union said it expects about 260 jobs to go, with redundancies beginning in May.
The Scottish government has said it will offer practical support to those who lose their jobs.
Bob McGregor, Unite regional officer, said: “So much has been done to save these yards until now.
“The workers there have fought for their future and it is difficult to believe that it can now be snatched away from them.
“The closures of these yards will turn these areas into an industrial graveyard.”
BiFab operates the yards at Burntisland and Arnish in Lewis. The marine engineering company had reached an agreement with business partners in November last year to receive payments to alleviate its immediate cash flow issues.
At that time, workers marched on the Scottish Parliament in Edinburgh over fears of job losses.
