EDF Energy has chosen its preferred bidder for the £2billion contract to build Hinkley Point C nuclear power station.
It is a joint venture comprising French civil engineering giant Bouygues Construction and the UK’s largest private construction firm, Laing O’Rouke.
EDF says the work, which is subject to planning consent, could create 4,000 jobs.
Before signing the contract, the two firms have made a preliminary agreement to work on a detailed design and construction methodology.
An EDF spokesman said: “This contract is the first relating to the main construction works which will see up to 25,000 jobs created on site over the course of the project, including an estimated 400 apprenticeships for the civils work.
“EDF Energy expects further apprenticeships and skills development opportunities in other parts of the project and is already working closely with local colleges, future employers and our trades union partners to ensure long term up-skilling of local and wider supply chains as a result of the project.
“The civils contractor will fully support and be engaged in these education and training initiatives.”
EDF Energy chief executive Vincent de Rivaz said: “I am delighted to welcome Bouygues TP/Laing O’Rourke Joint Venture into our project.
"The agreements announced today show we are continuing to maintain momentum in 2012 towards our final investment decision.”