A temporary desalination plant will have to be installed to provide enough water during the construction of Sizewell C if the £20billion nuclear power plant gets the go-ahead.

Consultation is under way on the plans for the unit, which would take sea water and remove the salt to create drinking quality water, because water companies cannot guarantee supplies.

But opponents of the power project say until the desalination plant is ready it will mean 40 more trucks a day visiting the site to deliver potable water.

Paul Collins, chair of Stop Sizewell C, said: "This latest consultation is yet another example of EDF trying to fit the square peg of Sizewell C into the round hole of East Suffolk.

"It exemplifies how wrong this project is for our area, lacking the necessary infrastructure, and calls into question what other last minute changes and additions EDF will demand as the obstacles of this wrongly-sited project emerge.

East Anglian Daily Times: Paul Collins, chair of Stop Sizewell CPaul Collins, chair of Stop Sizewell C

"The issue of fresh water supplies has been raised since the start. EDF's claims that a water desalinisation plant and its diesel generator power supply, plus 40 additional tankers of water a day for the first 9 to 12 months, won't mean increases in HGVs and CO2 emissions are not credible. And we are gravely concerned its operation would further damage the beach, impact coastal processes and create a toxic environment for local marine life."

A Sizewell C spokesperson said: "Clean water from a dependable source would be required from the earliest stages of construction of Sizewell C.

"While our planning application includes proposals to access water from a permanent water main, ongoing work with stakeholders throughout this time, including the water companies has indicated that there could now be a risk that the full requirement of potable water in the early years of construction will not be met.

"We are proposing a change to our planning application to include a temporary desalination plant on the main construction site, away from both Sizewell Marshes SSSI and Sizewell beach.

"The proposed temporary desalination plant would provide a reliable, continuous source of water while the permanent water transfer main is completed

"During the 4-6 months it would take to build the temporary desalination plant, clean water would be delivered to the Sizewell C site by water tanker trucks. This would not increase the overall number of HGVs predicted for the project during the early years of construction.

"The construction and operation of Sizewell C, including this proposed change to our construction Water Supply Strategy, will not impact the local supply of drinking water.

"When things change it is important that we listen and make changes. In that way we work to achieve planning consent for a project that reduces as much of the impacts of construction on local communities as possible."