The growth in offshore wind farms, a central part of the Government's fight against global warming, poses a potentially devastating threat to whales and dolphins, a report said yesterday.

Noise during construction - such as pile driving - can be heard by marine creatures in shallow water up to 80km away, damage their hearing at close range and causing dramatic changes to behaviour at distances of 20km.

The laying of cables and disturbances caused by service boats means the acoustic impact continues long after the building is over, the Whale and Dolphin Society said. Only five wind farms are in operation in the UK although seven are under construction with 14 more planned. By 2020, offshore wind power is expected to account for 20 per cent of the UK's energy needs.