Wind farms generating enough electricity to supply three million homes could be established off the Scottish coast after The Crown Estate approved key preliminary bids from a clutch of power companies.

If built, ten wind parks featuring hundreds of turbines could generate as much as 6,000 megawatts of electricity, a step towards the Government's ambition to provide 15 per cent of the UK's energy from renewable sources by 2020.

Four of the proposed wind farms - Beatrice, Bell Rock, Islay and Kintyre - were awarded to consortiums including Scottish and Southern Energy (SSE). They alone could have a combined capacity of up to 2,700 MWs. The proposed Kintyre wind farm would have up to 126 turbines covering about 70 sq km; another off Islay would have 138 turbines covering 93 sq km.

E.ON, ScottishPower, RWE npower and Mainstream Renewable Power were among other companies also awarded rights to start development of the schemes.

The exclusivity agreements made with The Crown Estate, which owns the seabed out to 12 nautical miles from the coastline of the UK, allow developers to begin initial survey and consultation processes. The Crown Estate is expected to award lease agreements for the sites next year.

However, experts have questioned whether the wind farms will ever be built without fresh government incentives to make them more viable. Industry analysts say that the cost of building offshore wind farms stands at about £3million per megawatt of installed capacity, suggesting that the price of building 6,000MWs could top £18billion.

Conventional power-generating equipment costs a fraction of this. Gas-fired power stations, for example, cost about £500,000 per megawatt - or one sixth in terms of the electricity generated.

This month, the Government granted approval for a gas-fired power station in Pembroke, West Wales, that will generate 2,000 MWs of electricity at a cost of only £1billion.

Wind farms are also unpredictable in terms of the amounts of power that they can produce, while the cost of attaching remote farms to the National Grid incurs additional costs.

Chris Stubbs, a director at WSP Energy, the consultancy, doubted that the projects would be built without government action to improve the economics of offshore wind power generation.

“It's great that people are interested in offshore wind, but the truth is that there is every chance these projects will be put on hold unless the Government is willing to intervene,” Mr Stubbs said.

Britain generates about three gigawatts of energy from wind farms, enough to power more than 1.5million homes. The Government estimates that the UK will need to boost this to 28 GWs to hit its 2020 target.

“The award of ten exclusivity agreements is excellent news for the companies involved, The Crown Estate and for Scotland,” Rob Hastings, marine estate director for The Crown Estate, said.

Peter Raftery, general manager of UK offshore development for Airtricity, SSE's renewable energy unit, said: “We believe that Scottish territorial waters represent an outstanding renewable resource and I look forward to the development of the sites.”

Leases that enable the developers to go ahead with construction work will be granted by The Crown Estate only once the developer has obtained statutory consents and permissions from the Scottish Government, which at present is conducting a strategic environmental assessment (SEA) for offshore wind within Scottish territorial waters. The SEA is expected to be completed around the end of this year.

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