Chancellor Rachel Reeves will unveil the long-awaited funding boost at the GMB Congress today, ending years of uncertainty around the Suffolk project.

She has been able to find the extra billions for Sizewell C through a change to her fiscal rules. This has made £113bn available for extra capital spending across government, funded by borrowing.

The Government’s nuclear power station building partner EDF still needs to secure financial support from private investors before the final investment decision is made next month.

The twin-reactor plant will generate enough power for six million homes and is expected to support 1,500 apprenticeships and thousands more jobs across the UK supply chain.

Around £330m of contracts have already been signed off with local firms, with 70% of the total predicted to go to British suppliers.

Reeves said: “Today we are once again investing in Britain’s renewal, with the biggest nuclear building programme in a generation. This landmark decision is our Plan for Change in action.”

Sizewell C has been on the drawing board since 2009 but was repeatedly stalled under previous governments.

Because the power station is a near replica of Hinkley Point C, the plan is to use the main supply chain companies from the new Suffolk project.

Its confirmation signals a major shift in policy, with the Government also preparing to back one of Europe’s first small modular reactor (SMR) fleets and investing £2.5bn into fusion energy R&D.

Once operational, Sizewell C and Hinkley Point C will be joined by SMRs to deliver more nuclear power than the UK has built in the last 50 years combined.

To secure the UK as a leader in both civil and defence nuclear, the government will also be investing £4 billion over the next decade in the Plymouth naval base.

The wider nuclear drive includes £6bn investment in the submarine industrial base at Barrow and Derby, and a £420m injection into Sheffield Forgemasters, helping to secure over 1,600 jobs.