Campaigners fear the Tories are set to snub British workers and award a £1.6billion defence deal to a Spanish-led bid.
The Government is poised to announce the winner of a competition to build three, 40,000-tonne Fleet Solid Support ships to resupply Royal Navy vessels at sea.
A decision is expected within weeks - and if the contract goes to a consortium spearheaded by a company based abroad it will be the first time British warships have been built overseas.
