Prospect, the largest union for engineers, scientists, specialists and professionals in the UK’s energy and nuclear industry said the government’s decision to further delay the project was incomprehensible.

The union's deputy general secretary Garry Graham said: “The new energy minister has talked about the importance of an industrial strategy which supports and underpins UK energy policy.

“The new Chancellor has talked about the importance of Hinkley Point C. Both have stressed that Britain is open for business and keen to attract investment in business and infrastructure.”

Prospect will write to the Prime Minister today seeking an urgent meeting.

The decision has to be seen in the context of the previous administration’s withdrawal of support for carbon capture, solar and wind at short notice, said Graham.

“We described those decisions, which came as a shock to the business and investment communities, as sending a chill wind through the sector in terms of investor and business confidence.

“Energy margins continue to decline – we are already asking intensive users to come off supply at periods of peak demand and relying on polluting diesel generation to keep the lights on.

“It is not only 25,000 high-quality jobs that are at risk, but the UK’s ability to keep the lights on and meet our climate change targets.

“It is incomprehensible that ministers and officials are not familiar with the deal hammered out with EDF over a number of years.

“At best the decision looks chaotic. At worst it appears that UK government is not a reliable or trustworthy partner,” he concluded.