The UK now boasts 6GW of wind energy capacity, enough to provide power to over 3.3 million homes, according to the latest update from trade association RenewableUK.

The group confirmed last night that the 6GW threshold had been passed after it was announced that the Ormonde offshore wind farm off the coast of Cumbria now has 120MW of capacity operational.

"This is a landmark achievement," said RenewableUK's Chief Executive, Maria McCaffery. "There's a great feeling of pride throughout the industry that we've reached a record high of 6GW, and there's a further 19.5GW of capacity under construction, consented, or in planning."

She added that the industry remained confident that it could deliver on the target set out in the government's renewable energy roadmap for 31GW of onshore and offshore wind capacity to be in place by 2020.

"The government's Renewable Energy Roadmap is calling for 31GW of onshore and offshore wind combined by 2020, and we're confident that we can deliver this if we continue to get the right level of government support," she said.

Speaking at RenewableUK's annual parliamentary reception last night, Chief Secretary to the Treasury Danny Alexander said the government remained fully committed to accelerating the expansion of the UK's wind energy sector.

"Working together, we can reach even greater heights," he said. "We are eager to ensure that the UK becomes the natural home for the most innovative, ambitious and inspiring renewable energy companies in the world, and we will continue to work with the industry to drive down costs and encourage even stronger growth in the years to come."

The report came on the same day as a controversial report from the centre-right thinktank Policy Exchange, which called on the government to ditch its renewable energy targets and its support for offshore wind energy on the grounds that it would add £400 to household costs by 2020.

The report was dismissed by the government as "flawed", but in a remarkable intervention Energy and Climate Change Secretary Chris Huhne labelled the study as "nonsense on stilts".

Writing during an online question and answer session hosted by Which?, Huhne responded to a question on the report with a stinging attack on the Policy Exchange's methodologies and motives for releasing the report.

"There is no such increase in the cost to families, but what there are is a load of rather silly thinktanks trying to differentiate themselves in a crowded market by coming up with wild and woolly estimates to get headlines in the Daily Mail and the Daily Telegraph," he wrote.

"They would save an awful lot of people some high blood pressure moments if their so-called economists bothered to pop in to DECC and get put right on some elementary A-level howlers. All our figures are there to see on the website, and we are committed to updating them every year. We have SAVED families money compared with the last government by removing the levies for carbon capture and storage and the renewable heat incentive. Overall, the impact of our policies on bills in 2020 is estimated to CUT bills by seven per cent."