About 5% of the UK’s electricity generation could come from a 10-mile long Severn barrage now being considered by the government.

If the £15bn tidal hydro-electric structure gets the go-ahead, Britain would have to find another 10% of its generation from renewable sources to meet the total 15% by 2020 target set by the latest European Union proposals. At the moment just over 2% of Britain’s generation is from renewables.

In the same week the revised EU targets were announced, energy secretary John Hutton published the terms of reference for a two-year feasibility study of the environmental, social and economic impacts of a barrage.

A public consultation on the 8.6GW hydro-electric barrage, from Weston-Super-Mare to Cardiff, could come as early as 2010. A smaller, 1GW barrage further upstream is also a possibility.

The Severn Estuary’s tidal range, one of the world’s highest, is up to 14m (42ft). Water would be impounded on a high tide and at low tide would pass through sluices incorporating fan generators.