Brussels demands thousands more wind turbines across the UK

Energy experts say new EU climate change targets mean the UK will have to generate 40 per cent of its electricity from green sources within 12 years.

In order to meet that target, the number of wind turbines on the land would have to rise fourfold. Thousands more would be needed at sea.

The move would be one of the greatest engineering projects in years - and dramatically change the skyline of Britain and its coastal waters.

But critics say onshore turbines are an expensive blot on the landscape that often fail to generate enough power to justify their existence.

The Government concedes that the shift away from coal and gas will cost up to £6billion a year. Most of that burden will be passed to consumers.

The move is part of the EU's commitment to generating 20 per cent of Europe's energy from renewable sources by 2020.

Under the plans - approved by Tony Blair - every member state will be told its contribution to the "green energy revolution" tomorrow. Britain currently has one of the worst records for renewable energy in Europe.

Years of cheap gas mean that nine out of ten homes use gas central heating, while hydroelectric and wind power produces just 2 per cent of electricity.

Tomorrow, Brussels is expected to demand that 15 per cent of Britain's energy, including heating, transport fuel and electricity, comes from renewable sources by 2020. Because it would cost too much to convert homes and vehicles to green energy, the bulk of the target will have to be met by electricity companies.

The Department for Environment, Food and Rural Affairs estimates that 40 per cent of electricity will have to be renewable within 12 years.

If it fails to meet the targets - described by civil servants as "difficult" - Europe will impose daily fines on the UK.

Around 5 per cent could come from tidal power if the Government is allowed to build the controversial Severn Barrage, the hydroelectric generator planned to cross the Severn Estuary. A few per cent could come from burning biomass - such as wood or crops - in power stations.

But given the short timescale, most will have to come from wind. The wind energy industry reckons it will need at least 7,000 turbines on land to meet the target. Today there are 1,910.

The Government has already unveiled plans to build huge wind farms off the coast of Britain. However, the energy industry says the number of onshore turbines will also need to rise.

British Wind Energy Association spokesman Chris Tomlinson said: "It's quite a challenge - and it will depend a lot on the public's acceptance of onshore wind turbines.

"In the early 1990s, they tended to be sited on tops of hills and so they were in full view. However, now the technology has improved so that they can be taken down from hills and sited in valleys."