Details of a feasibility study into the Severn Barrage, a tidal power plan that could provide about 5% of UK electricity, have been announced.

The study is expected to last two years and will conclude with a full public consultation in 2010.

The barrage could extend from the South Wales coast to Weston-super-Mare. Business secretary John Hutton said: “The Severn Estuary has some of the best tidal potential in the worldâ?¦ We must understand the cost and the impact that a project of this scale could have – not least the environmental, social and economic effects.

Some environmental groups have warned that a barrage could have an adverse effect on wildlife. The Royal Society for the Protection of Birds said it would put thousands of birds, salmon and other fish at risk. The estuary contains mudflats, saltmarshes, rocky islands and food that supports some 65,000 birds in winter.

Mr Hutton said the study would recognise the nature conservation significance of the estuary.