At least 200 jobs will be created at a Cumbria shipyard after the go-ahead for initial work to begin on the Trident nuclear weapons system replacement.
The Defence Secretary Liam Fox approved the £3bn first design stage for replacement submarines.
BAE Systems, in Barrow, will be involved in the design contract and said more than 200 people would initially be recruited.
The posts will be in engineering and project management.
A final decision about the project has been delayed until 2016 and a review into alternative deterrent options will also be carried out.
BAE managing director John Hudson said: "We are pleased that the Ministry of Defence has placed this important design contract with us, along with our industrial partners, Rolls Royce and Babcock Marine.
"Submarine design remains a demanding technical challenge.
"We currently employ around 5,000 employees and this contract is important in sustaining and developing our skilled workforce, initially in engineering and project management."
The review into alternative deterrent options will be overseen by Liberal Democrat Armed Forces minister Nick Harvey.
Barrow Labour MP John Woodcock welcomed the news about the initial work.
But he said he was concerned about the review and that it was being overseen by the Lib Dems, who have been sceptical about Trident renewal and argued for other options to be looked at.
Mr Woodcock said: "I think workers in Barrow shipyard are going to listen with alarm to the prospect that there is going to be yet another review into the feasibility and studying alternative options."