Union leaders have urged politicians and shipbuilding bosses to act now to prevent the closure of yards with the loss of thousands of jobs.
A leaked memo has reportedly revealed plans which could see two British shipyards close.
The memo says that the Ministry of Defence is willing to finance redundancies in order to scale down Britain’s capacity for building warships.
And it shows BVT Surface Fleet’s chief executive Alan Johnston forecasting savings of as much as half a billion pounds from the closure of two out of the three yards after the contract for two aircraft carriers is completed in 2014.
The memo setting out the plans was reportedly sent from the chief executive of the Govan and Scotstoun yards in Glasgow to senior executives at owner BVT Surface Fleet which also has an operation in Portsmouth.
Jim Moohan, GMB Scotland senior organiser, said the news had come as a “massive shock”.
“For the first time we had turned a corner with a golden future for the next five to 10 years. This announcement is being timed quite cynically and deliberately to mark the card of employees in shipbuilding within the UK that the reduced capacity is going to result in problems.”
Mr Moohan said: “If I’ve got five years’ notice to try and save an industry or protect it, then that gives me and others and opportunity to do so,” he said.
The firm employs 7,000 workers at the two Glasgow yards and Portsmouth, as well as at another location in Bristol.
A BVT spokesman said that he could “not deny” that a memo existed.