The firm will deliver key road schemes early in 2025 for the vast project.

The latest contract award was announced as Sizewell C confirmed it has already signed £2.5bn worth of contracts for the project spread around nearly 300 UK suppliers.

Pre-construction work and early enabling works got underway at the Suffolk site around 12 months ago after development consent.

Now the industry is waiting for the Treasury to approve the final business case, expected in the Spring spending revenue.

Sources close to talks between the Government and nuclear power generator EDF are reported to put the latest forecast cost estimate at £40bn, double the initial estimate provided by the power company.

The UK government and the EDF will fund about 40% of the Sizewell C project. Government officials are now gauging interest from private investors to meet the rest of the costs.

EDF yesterday issued a statement denying forecast project costs were so high.

“Recent claims about Sizewell C’s costs are not accurate and do not reflect the significant savings we are already making because we are building on the achievements at Hinkley Point C,” said EDF.

“That project has done the hard job of restarting UK nuclear construction and is seeing efficiency improvements of around 30% between its first and second reactor units.

“It means we are starting construction with a completed design, a skilled workforce and a supply chain ready to deliver.”

The 3.2GW nuclear power project will see UK firms deliver around 70% of construction value and support 70,000 high-quality jobs.

The project has already made significant progress across its main development site, including archaeology and earthworks, as well as the preparatory work for its concrete batching plant and temporary desalination plant.

New site offices on its Ancillary Construction Area are now complete, with enhancements to local road and rail infrastructure.

Julia Pyke and Nigel Cann, joint managing directors of Sizewell C, said: “It’s been an incredible first year of construction for Sizewell C.

“We’ve now got around 1,000 people driving this project forward both on our main development site and off-site infrastructure, and we’ll have around 2000 people by the end of the year with around double the amount of apprentices.

“We’re making big gains with early manufacturing, with equipment already 20% through manufacture. That means we’re already able to deliver significant contract value to suppliers and drive growth right here in the UK.

“Building on the work of Hinkley Point C, we have a fixed design and a capable and industrialised supply chain in place, and that gives us a big advantage when it comes to cost certainty and clarity of schedule.

“A year down the line of formal construction, we’re in a very strong position to deliver a project that will provide lower bills and clean energy to six million homes, thousands of good jobs, and energy security for Britain.”