Sue Ferns, Prospect senior deputy general secretary, said:

“It is welcome news for the nuclear industry and testament to the hard work of union members that construction at Hinkley C is progressing so well.

“Hitting milestones on time like this is a key indicator of the viability of new nuclear. Learning lessons and transferring skills from this to other new nuclear projects will enable the UK to keep costs down.

“We have committed to a zero-carbon future and new nuclear must play a part in the low-carbon energy generation we need. If we are to come anywhere close to hitting our targets Government policy needs to be clearer and much more ambitious.”