The steel is likely to be sourced from the French firm Industeel. Defence Secretary Michael Fallon is expected to give the £41 billion ($52 billion) Successor program the green light on Thursday.
The UK steel industry looks increasingly precarious in the face of cheaper Chinese alloy and favorable tax rates for European rivals.
“The Government has said time and time again that big infrastructure projects should make the most of British steel, yet here we have the Defence Secretary boasting about cutting steel that was made abroad,” Roy Rickhuss, General Secretary of steelworkers’ union Community, told the Telegraph.
“It’s a slap in the face to hard pressed British steelworkers.”
He said the Successor program should be “a fantastic project that will support British manufacturing” and urged the government to use UK steel at every opportunity.
Deals have not yet been finalized and BAE Systems, the arms firm which runs the Barrow-In-Furness facility where the vessels would be built, has not commented.
However, a source close to the firm told the Telegraph: “On the pressure hull steel, we expect to buy from Industeel in France who provide the quality we need.”
Successor is the replacement submarine to the Vanguard Class. It was rubberstamped in July when parliament voted to renew the controversial Trident nuclear weapons system.
The vote, which ratified plans underlined in the 2015 Strategic Defence and Security Review, authorizes the construction of four submarines to replace the aging fleet at an estimated cost of £41 billion.