The government has officially given the green light to build Sizewell C after signing off a final investment deal based on a £38bn construction cost.

Energy secretary Ed Miliband has signed the final investment decision, ending more than a decade of delays and securing a landmark project expected to power six million homes and support 10,000 jobs during peak construction.

The state will take a 44.9% stake in the Suffolk twin-reactor scheme, making it the single largest shareholder.

Backers include Centrica, which is investing £1.3bn for a 15% share, alongside La Caisse (20%), EDF (12.5%) and Amber Infrastructure (7.6%).

The National Wealth Fund will provide most of the project’s debt finance, alongside backing from France’s Bpifrance Assurance Export.

Construction is estimated to cost £38bn, around 20% cheaper than the near-identical Hinkley Point C project.

The savings will come from using the Hinkley C supply chain and efficiency gains from lessons learned on the delivery.

The total equity and debt finance made available exceeds the target construction cost to help safeguard taxpayers in case of overruns.

This morning the Government added the project supply chain would be strongly incentivised to keep costs down and investors would lose potential revenue if there were overruns, reducing risk for taxpayers.

The Government is employing a regulated asset base (RAB) funding model that caps the impact of the project on household energy bills to around £1/month during the build phase. Once operational in the 2030s, Sizewell C is forecast to save the electricity system £2bn a year.

Sizewell C is already ramping up supply chain activity, with £330m in contracts signed so far and 70% of the total spend expected to go to British businesses.

The deal allows construction activity to ramp up bring a huge boost to the civils sector.

Sizewell C anticipates working with more than 3,500 UK firms. Around £4.4bn of value is earmarked for the East of England alone. The project will also create 1,500 apprenticeships.