Britain is to launch a huge expansion of offshore wind-power with plans for thousands of turbines in the North Sea, Irish Sea and around the coast of Scotland.

John Hutton, the energy secretary, will this week announce plans to build enough turbines to generate nearly half Britain’s current electricity consumption. He will open the whole of Britain’s continental shelf to development, apart from areas vital for shipping and fishing.

The scheme could see turbines so large that they would reach 850ft into the sky, nearly 100ft taller than Canary Wharf. Each would be capable of powering up to 8,000 homes.

Britain’s current range of coal, gas, nuclear and other power stations are capable of generating 75 gigawatts (GW) of electricity, but less than 0.5GW comes from wind. Planning consents have been granted for a further 3GW and the government had already made clear it wanted this raised to 8GW.

Hutton will announce at an energy conference in Berlin tomorrow that he wants to see this target raised to 33GW-worth of wind turbines installed in the seas around Britain by 2020. If energy consumption remains stable this would mean wind power could supply the electricity needs of every home in Britain.

There would still be a need to keep fossil-fuelled power stations in reserve because windless days could leave Britain with power shortages.

However, studies at Hutton’s department for business, enterprise and regulatory reform have shown that the extra cost of maintaining standby power stations would add little to bills.

Hutton said: “The UK is now the number one location for investment in offshore wind in the world and next year we will overtake Denmark as the country with the most offshore wind capacity.

“This could be a major contribution towards meeting the EU’s target of 20% of energy from renewable sources by 2020.”

Hutton made clear the scale of the plans. The “first round” of offshore wind farms, in 2001, comprised a few small demonstration projects. The “second round” in 2003 limited development to the Thames estuary, the Greater Wash and the northwest.

Under the new proposals, the whole of Britain’s continental shelf would be opened to development, potentially including the English Channel and much of the coast of northern Scotland, where winds are most reliable.

It could mean that wind farms would become visible from almost every point of Britain’s coast. Some developers have made clear that they would like to see a forest of turbines stretching up the North Sea, whose shallow waters make it relatively cheap and easy to develop.

Hutton’s plan would be subject to an environmental assessment but it is certain to amplify the conflicts over wind farms.

So far there have been few objections to Britain’s six offshore wind farms because they are largely out of sight.

However, the scale of the proposed offshore developments is certain to bring controversy as they will often be visible from land.

Maria McCaffery, chief executive of the British Wind Energy Association, welcomed the move. “This expansion will mean that by 2015 the UK’s offshore market will be twice the size of any other national offshore wind market.”

Times recommends

• Energy-saving ideas from switched-on professor
• Rooks are as clever with tools as chimpanzees
• Burping of the lambs blows roast off menu