Britain’s coastal waters have space for up to 7,000 more wind turbines than are already planned, according to an environmental audit of the likely impact of offshore wind farms on wildlife.

The assessment was made as part of preparations for the third phase of offshore wind farm development around the country.

The 5,000 to 7,000 turbines recommended by the report would be enough to supply almost every home in Britain with electricity.

They are intended to form part of a 33-gigawatt offshore electricity supply planned by the Government to ensure that Britain meets it renewable energy and carbon-emission reduction targets. However, the future of the project has been cast into doubt recently because of concerns about rising costs.

Plans for 341 turbines in the Thames Estuary, the London Array project, could cost more per megawatt produced than a nuclear plant. Shell pulled out last year and there were further doubts about the project’s likely profitability last week.

Ed Miliband, the Energy Secretary, was nevertheless bullish about the prospects of offshore wind farms as the government-commissioned report into the environmental impact was launched.

“In terms of electricity, offshore wind power could potentially make the single biggest contribution to our 2020 renewable energy target so it’s vital we maximise the UK’s natural resources to help in the fight against climate change,” he said.

“This report provides a real advance in our understanding of the ecology and geology of the UK marine environment so we can continue to ensure that projects like wind farms are built in the most suitable places.”

The Environment Report is now the subject of a 12-week period of public consultation. It addressed a variety of issues, including the likely impact of the turbines on the seabed, birds, seals, and fish stocks.

Rob Hastings, director of the marine estate at the Crown Estate, which is the landlord of the seabed, said: “The publication of the study at this time ensures that as an industry we are well prepared to take on the challenges that will come as part of the round-three offshore wind farm leasing process.”

Seven offshore wind farms have been built in British waters and five more are under construction. A further nine have been approved.

Wind farms are seen as a crucial element in Britain’s effort to meet its target of providing 15 per cent of energy from renewable sources because the technology is tried and tested. The country and its waters are among the windiest in Europe.

Nick Rau, of Friends of the Earth, said: “We’re delighted that the Government has confirmed the massive potential for offshore wind energy — it must now make sure that it becomes a reality.”

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