It will be located 12 miles off the coast between Margate in East Kent and Clacton in Essex and consist of 341 turbines spread over 90 square miles, making it the world’s largest offshore wind farm.

The Chamber of Shipping said that the decision had been rushed through by the Department of Trade and Industry without proper consideration of the risks to mariners. More than 100 ships a day would pass close to the wind farm.

The chamber said that the wind farm would be too close to shipping lanes, leaving little margin for error. It said the turbines would interfere with radar, preventing ships from spotting smaller boats.

“With visual and radar detection of vessels impaired, the risk of collision is increased, and should such a collision involve a chemical or oil tanker, the repercussions would be immediate and far-reaching.

“The decision ignores expert advice on the safety of those using the estuary [and] disregards the Maritime and Coastguard Agency’s guidance as to the minimum distance which should separate shipping lanes from wind farm sites. It is hard to understand why an environmentally minded project has been pushed forward with little consideration given to its potential to cause an irreversibly damaging environmental disaster.”

A spokesman for the DTI said that the approval contained a condition that required more work to be done on navigational safety.

A second wind farm, also approved yesterday, will comprise 100 turbines seven miles from the Kent coast near Margate.

The Thanet windfarm will be 7 miles from North Foreland on the Kent coast and will contain 100 turbines, occupying 13.5 square miles. The chamber said that the design of this windfarm had taken account of shipping.

The electricity generated by the two wind farms combined, a total of 1.3GW, will be enough to power a third of London's three million households, or all the homes in Kent and Sussex.

David Miliband, the Environment Secretary, said that the wind farms would contribute to the Government’s target of producing 20 per cent of Britain’s electricity from renewable sources by 2020. He said: “At the moment we are about between 4 per cent and 5 per cent and this will take us another per cent or so towards that target of 20 per cent.”

The larger wind farm, London Array, is being built by a consortium including Shell. It will cost £1.5 billion. The Royal Society for the Protection of Birds withdrew its objection after receiving assurances about the impact on a colony of 7,000 red-throated divers.

Greenpeace welcomed the Government’s decision: “This is clean energy on a massive scale. It’s a pioneering project and we need more of them.”

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