The TUC and general secretaries of major trade unions have warned that the Sizewell C nuclear power station project may be at risk if delays to decisions around government funding continue.

The consortium, including the GMB union, has penned a letter to the business secretary, Kwasi Kwarteng, urging a decision to be made in getting funding signed off for the proposed twin reactor on the Suffolk coast.

The letter warns the government's funding model, the Regulated Asset Base model (RAB), won't work until a government Investment Decision (GID) is confirmed.

The letter says: “We sincerely believe that unless this matter is resolved in the next few weeks, the UK’s nuclear future and the jobs and skills of tens of thousands of nuclear workers will be at risk."

GMB general secretary Gary Smith said: “There can be no net-zero without new nuclear, so why does this government keep dithering on the big decisions to secure our clean energy future?

“Their indecision is putting the vital new Sizewell reactor at risk."

Senior deputy general secretary of trade union Prospect said: "The Government must now get moving on an investment decision that will be good for energy security, good for jobs and skills, and hugely important in tackling climate change.”

General secretary of trade union Unite, Sharon Graham, said: "The workers are committed to making this facility a success. If the project is put in danger, then the blame will lie firmly with the government.

“Let’s be clear, every day of delay puts energy jobs at risk and hampers the nation’s progress to a mixed energy model. The Government needs to get its act together and move this build forward, now.”

However, Alison Downes, from campaign group Stop Sizewell C, said: "The unions can threaten all they like, but it would be total folly for the government to commit taxpayers' money to Sizewell C when EDF's plans have more holes than a swiss cheese, and with so many important regulatory hurdles to overcome.

"That's quite apart from projects using the same reactor technology being in dire trouble elsewhere. It's s almost a year since China's Taishan 1 was turned off and Finland's supply of electricity to the grid has been delayed yet again despite construction starting 17 years ago.

"EDF staff were forced to distance themselves from the unions' letter but must be feeling pretty jumpy. It would be a farce if the government took any shortcuts."