Researchers are questioning whether the winds of change are blowing hard enough to meet the UK's energy needs, despite trade and industry secretary Patricia Hewitt's commitment to wind power. Ms Hewitt this week opened the second round of bids from developers for offshore wind power projects, expected to be worth up to ?7.5 billion.

Two and a half years ago the first round saw 17 sites let. Yet today the only site under active development is on the coast at Prestatyn, North Wales.

Robert Gross, lecturer in energy policy at Imperial College London, said:

"Developers are finding it difficult to raise funds because of the risk.

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It's never been tried before. The real question is whether the government has put enough policy commitment behind it. The majority of the world's scientists are agreed that climate change is real.

"The key to tackling it is innovation. But this doesn't happen by magic - companies invest, learn from experience, and reduce their costs. The government needs to build on current policies and do more to encourage the private sector to innovate," he said.

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Renewable energy, such as wind power, does not emit carbon compounds so it is a key part of the government's strategy to reduce carbon emissions. The government hopes to increase power generated from renewable sources to as much as 20 per cent by 2020. Lord May of Oxford, president of the Royal Society, said: "The government's own figures show that even if we achieve the ambitious target of generating 10 per cent of our electricity from renewable sources by 2010, we will be more reliant on fossil fuels than we are now because of the rapid decline in nuclear power. Renewable energy is being phased in more slowly than nuclear power is being phased out, and the government expects to make up the shortfall by burning more gas."

Ian Fells, who sat on the Royal Society and Royal Academy of Engineering committees advising the government on energy policy, said: "If you took all the wind farms built in the world over the last 20 years you would still not meet this target. To get 20 per cent by 2020 would require an extraordinary and heroic effort. But supposing you achieve it? By then, all but one nuclear power station will be decommissioned, which loses 20 per cent of your carbon-free capacity. You've run very fast to stand still."