Thousands more wind turbines could be built on blocked sites when new 'stealth' technology trialled in East Anglia becomes available next year.Across the UK, 5,000 turbines are on hold following objections from military and civil aviation authorities because they can interfere with important radar signals.

Thousands more wind turbines could be built on blocked sites when new 'stealth' technology trialled in East Anglia becomes available next year.

Across the UK, 5,000 turbines are on hold following objections from military and civil aviation authorities because they can interfere with important radar signals.

But, following 'successful' trials in Norfolk last year, a seven figure scheme to develop new 'stealth' turbines that ease the problem is well under way, which could reopen the door for many of the stalled bids.

Dr Dave Moore is business lead for the scheme for defence technology specialists QinetiQ, , who are working with turbine suppliers Vestas.

'At the moment 5,000 turbines are blocked because of this issue and it is increasing. It is a major threat to the UK being able to meet its renewable energy targets by 2020,' said Dr Moore, who is from Norfolk.

The UK is said to be the windiest country in Europe and the government wants 15pc of our energy needs to be met by renewable green sources - the lion's share of which is expected to come from wind - by 2020.

Currently this country has about 4GW, both onshore and offshore, of installed capacity but is estimated to need 33GW by 2020 to meet its target - several thousand more turbines - which is a cause of major concern for anti-wind campaigners.

The new 'stealth' turbines feature radar absorbing materials (RAM) integrated into the manufacturing processes for the components - blades, nacelle and tower - which cuts the interference they can cause to the point where they can be effectively 'factored out' of air traffic control and air defence systems.

The current project has grown out of a multi-million pound scheme, part funded by the government, which ended last year following the trial of stealth blade at North Pickenham.

James Beal, managing director of Renewables East, which is charged with pushing the region's renewables industry forward, said: 'Stealth turbines are good news for the wind industry. It unblights an awful lot of the country, although it is only part of the problem solved.'

Brian Kidd, chairman of the Campaign Against Turbines at Shipdham and Scarning (CATSS), said: 'If it can get rid of the problem then I suppose wind turbines that are held up by objections from the Ministry of Defence and civil airports will go ahead but I suspect they will need to complete a lot more trials to prove its effectiveness.'