Fears have been voiced that the next stage of consultation on the proposed nuclear power plant may not now take place until the autumn.

The setback is due to concerns expressed by unions in France over EDF Energy’s bid to build an £18billion reactor at Hinkley Point – with the unions now to be formally consulted over the project and its financing.

EDF has consistently said Sizewell C cannot move forward until a final investment decision is made on the Somerset power plant. It was hoped this would happen in May but now it looks likely that a 60-day consultation with unions will be necessary.

The first round of consultation on Sizewell C took place in 2012 and communities have complained that the lack of further information since then on issues such as the location of the workers’ accommodation complex, park and ride sites, and road and rail links have left them “in limbo”.

Suffolk Coastal MP Therese Coffey said: “It was disappointing to learn that trade unions are considering challenging EDF on its British nuclear programme – French trade unions that is.

“I really had hoped that the final investment decision on Hinkley Point would be made next month, allowing consultation on Sizewell C to start by the summer.

“The further consultation for unions means that we are unlikely to move to the next stage until September. Meanwhile, MPs and councils continue to work on this huge project which will bring huge benefits to the Suffolk coast.”