"This is the first ever contract relating to main construction works on any site where a new nuclear plant will be built," said Prospect General Secretary Designate Mike Clancy. "It is a significant step towards the first nuclear plant in 20 years being built in the UK."

The construction consortium will immediately start work on developing the design of the Hinkley Point C power station and the construction programme, creating up to 4,000 jobs, most of which will be local.

Clancy said: "We hope the government will recognise this as a signal of serious commitment by EDF Energy to investing in new nuclear in Britain. But there are still several hurdles to jump through. The contract is subject to securing planning consent and EDF is making its final decision on investing in the UK at the end of the year.

"Much depends on the government ensuring that a clear and robust energy pricing mechanism is in place, so that any investment is guaranteed a proper return. That means stable energy prices, which can only be achieved if the government guarantees a mechanism that recognises the importance of nuclear in achieving a low-carbon economy."