The union described it as a betrayal of British shipbuilding and a huge deviation from the recently published National Shipbuilding Strategy.

The announcement comes at a time when workers at three yards employing Prospect members face immediate redundancies or uncertain futures.

Four hundred jobs are at risk at Rosyth Dockyard in Fife, hundreds of redundancies were announced at Devonport Dockyard in Devon recently and members at Portsmouth Dockyard also face an uncertain future.

"We welcome the questions raised in the House of Commons by Fife MP Douglas Chapman last week," said Richard Hardy, Prospect's national secretary for Scotland. "We are meeting with Douglas on 1st May to discuss the issue further."

Hardy described as "nonsensical" the prime minister's response that the National Shipbuilding Strategy would protect jobs and create a bright future for British shipbuilding.

He said: "The strategy itself explicitly states that the government should consider all the benefits of building at home, such as jobs both directly in the yards and in the supply chain, the impact on the public purse of avoiding benefit payments and the increases in tax revenues and innovation incentives. You don't protect jobs by placing contracts abroad when thousands of jobs are at risk here in the UK."

Hardy concluded: "It's not as if going for the bargain basement price doesn't have other substantial strategic risks; the recent tanker build in South Korea for the RFA saw delays and cost overruns, whereas the Queen Elizabeth was delivered on time by a combination of British yards."

Prospect will continue to fight for its members' jobs and a secure future for the British defence shipbuilding industry.