Sizewell C developer EDF is being asked by government whether a temporary desalination plant could last for the lifetime of the new nuclear power plant if it is built.

The public examination of the plans for the £20billion twin reactor on the Suffolk coast was told a permanent water supply for the proposed development had not yet been secured.

However, a temporary desalination plant would run during the construction of the project.

Kwasi Kwarteng, secretary of state at the Department of Business, Energy and Industrial Strategy, is now asking EDF what progress has been made on securing a permanent water supply solution.

But he also says: "The applicant should confirm if it would be possible for the proposed temporary desalination plant to permanently meet the full water supply demand for the lifetime of the proposed development should no alternative water supply solution be identified."

TASC (Together Against Sizewell C) said: "The mere suggestion that desalination, a process that EDF have previously discounted as too environmentally damaging, could be needed for the 60-year lifetime of the Sizewell C project, confirms TASC's view that the water supply strategy is unsustainable, one of the many reasons why the site is not suitable."

Mr Kwarteng has also asked if the two villages bypass on the A12 and the A12 to Sizewell link road can be built before construction starts on the main plant.

Charles Macdowell, of the B1122 Action Group, said: "We have been arguing for some time that EDF's plan to push up to 600 trucks a day down the current B1122, with no serious attempt to protect those along it, is crazy.

"This would go on for the first two or three years until the link road is built. It is good to see, in this new letter, that BEIS is sympathetic to our point-of-view that the link road should be built first, and we hope that EDF's response will take local feelings into account too."

A spokesperson for Sizewell C said: “As the planning application for Sizewell C progresses it is natural that government will raise questions with us, which we are addressing.”