A giant windfarm in the sea off Wells would have an “unacceptable impact” on the character of Norfolk's coastline, claims a council report.Concerns about the scale of Centrica's plans for the Docking Shoal windfarm, nine miles off the coast, are outlined in the planning officers' report.

A giant windfarm in the sea off Wells would have an “unacceptable impact” on the character of Norfolk's coastline, claims a council report.

Concerns about the scale of Centrica's plans for the Docking Shoal windfarm, nine miles off the coast, are outlined in the planning officers' report. West Norfolk councillors are being urged to lodge an objection to plans when they meet next month. But the ultimate power to approve or reject the proposals lies in Westminster and the local council is acting only as a consultee.

The report warns that the turbines could damage internationally important conservation areas in The Wash and rare species like the sandwich tern, which breed on Natural England's reserves at Scolt Head and Blakeney Point. It warns that up to 50 of the birds could perish each year in collisions with turbines.

A spokesman for the RSPB said: “The Docking Shoal windfarm is likely to cause problems for sandwich terns and this would be a concern for the RSPB. We look at windfarm applications on a case-by- case basis and this will also be true for Docking Shoal.”

The report said: “Given the scale and extent of the proposed Docking Shoal Offshore Windfarm, effects on the surrounding seascape and visual environment are unavoidable.”

Elizabeth Watson, councillor for Hunstanton, Holme, Old Hunstanton and Ringstead, said: “I am very unhappy that they do not know the exact numbers and there will be cumulative effect with the other windfarms along the coast. It is very much going to be a change in character of the whole area of north Norfolk. I am very uncomfortable with this decision being made in Westminster. They are not the ones who are going to have to live with it.”

The proposals are part of a government drive to source up to a fifth of Britain's energy needs from renewable sources by 2020.

The “Greater Wash” was identified by the Department of Trade and Industry as a strategic area for the development of offshore wind energy in 2002 and the crown estate, which owns the seabed, granted Centrica a lease for Docking Shoal in 2005.

In its application for Docking Shoal, the firm says it could build up to 160 turbines on the site, which stretches parallel with the coastline from Wells to Brancaster.

A spokesman for the Department of Energy and Climate Change said public notices had been published and exhibitions held for the turbines, so people were able to have their say.

She said: “The decision will be made by the secretary of state for energy and climate change, Ed Miliband, as the turbines will have a capacity of over 100 megawatts.

Alan Maclaughlin, spokesman for Centrica, said its experts would look at the council's objections in detail and would issue a full response.