Senior politicians in Wales and Westminster say a £15bn plan to build a barrage across the Severn Estuary could help solve the growing energy crisis.
The barrage would stretch 10 miles across the Bristol Channel
First Minister Rhodri Morgan and Welsh Secretary Peter Hain have backed plans for a barrage over the Bristol Channel.
The consortium behind one proposal says its 10-mile project would bring as much energy as three nuclear power stations.
Environmental groups fear a barrage over the estuary would destroy a unique and world-famous eco-system.
The Severn has a tidal range approaching 14m, the second highest in the world.
A tidal barrage has operated near St Malo in France for decades
The Severn Tidal Power Group (STPG), a joint venture between six power engineering and construction firms, estimates this can be harnessed to generate up to 6% of the electricity for England and Wales.
The group is proposing a barrage across the estuary from Lavernock Point, near Cardiff, to Brean Down in Somerset.
The scheme is different from one put to councillors in Somerset on 1 March by a Neath businessman.
The Welsh Assembly Government has now decided to submit its recommendations on the idea of a Severn barrage to the UK government's Energy Review next Tuesday.
Both Mr Morgan and Mr Hain have said they see a barrage across the Severn as one solution to the UK's energy crisis.
Roger Hull, of the Severn Tidal Power Group, said the barrage would take six years to build and could be generating power as early as 2017.
The tide would drive turbines like this one at La Rance, France
He said: "It's a proven technology. This is a big application because, of course, if you want to generate a lot of electricity, you need a big project to do so.
"It's definitely a good way of producing this predictable, renewable power that does not produce any carbon dioxide at all. So it's very climate friendly."
A tidal barrage has operated at La Rance, near St Malo in Brittany, since 1967.
But environmentalists claim a Severn barrage would adversely affect the ecology of the estuary, even ending the Severn bore.
Tim Stowe, of RSPB Cymru, said the 80,000 waterfowl - including dunlin and redshank - which the society estimates use the estuary as their winter feeding grounds would have to go elsewhere or perish.
He said: "The impact can only be negative on the birds that use it. Once you have built it, you cannot take it away."
The UK government is examining all forms of sustainable energy. It is aiming to generate 20% of Britain's energy needs using renewable energy sources, such as the wind and tides, by 2020.