Britain's so-called "dash for wind" means that it is now the biggest off shore generator – producing as much as the rest of the world put together.

But costs of building the farms have doubled due to spiralling prices for steel and the drop in the value of the pound.

The running costs are also increasing.

The report found that costs have risen for all kinds of generation but off shore wind farms remain by far the most expensive – 90 per cent more than fossil fuel generators and 50 per cent more than nuclear.

The news is bound to lead to question over the government's policy of using wind power to meet its target to generate around a third of its electricity from renewables by 2020.

But the authors of the report at the UK Energy Research Centre (UKERC), a government think tank, said they remained "cautiously optimistic" that wind can play a significant contribution to the zero carbon energy production for Britain.

"We think that there are grounds for cautious optimism," said Dr Robert Gross, of Imperial College London, who headed the report. "Yes it is more expensive than gas and coal and is unlikely to reach parity for at least 20 years but we still think it is a worthwhile energy producer.

"All alternatives such as nuclear and carbon capture are bound to have teething problems too."

With the opening of Thanet wind farm in the North Sea last week Britain became the biggest offshore wind generator in the world.

(Telegraph)

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