Staff at the BiFab marine engineering yards in Fife will be handed redundancy notices on Tuesday.
BiFab has yards at Methil, Burntisland and Arnish on the Isle of Lewis and was hauled back from the brink of administration in November.
Industry minister Keith Brown and First minister Nicola Sturgeon eventually managed to broker a deal involving all the major contractors to save the yards.
Management at the yards told the trades unions on Monday that they will be issuing redundancy notices to the core workforce on Tuesday.
Some 260 jobs are to go by early summer with the possible closure of the yards completely by the end of June.
These timescales can only be reversed if new contracts can be established for the yards.
Unite’s regional officer Bob McGregor said: “The closures of these yards will turn these areas into an industrial graveyard.