The Green Party has urged Energy Secretary Ed Miliband to drop plans for a massive tidal barrage across the River Severn and to develop more efficient green power sources instead. The idea is one of five short-listed for closer government scrutiny.
The proposed 10-mile barrage would stretch from Cardiff to Weston-super-Mare and cost £15 billion. Engineers claim it could provide 5% of all electricity consumed in England and Wales, equivalent to three nuclear power stations.
But environmentalists claim a Severn barrage would adversely affect the ecology of the estuary, an internationally-protected wildlife site. The Royal Society for the Protection of Birds said 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.
The Green Party said it was wholly committed to the development of renewable energy but that the proposed barrage would do more harm than good.
Ricky Knight, the Green Party's party's lead candidate for June's European Parliament election in the South West, said: "This barrage is an irresponsible and wasteful gamble."
Cllr. Knight continued: "Detailed reports have shown that this massively expensive and hugely damaging proposal cannot be justified on environmental or economic grounds - there are simply too many cheaper options for clean energy generation."
"Other viable technologies would be more practical, more flexible, offer better value-for-money and damage the environment less."
The Green Party's policy of opposing the barrage plans is endorsed by many other groups, such as the World Wildlife Fund, the National Trust, and Friends of the Earth.
Cllr. Knight added: "Long before other political parties caught up, the Green Party recognised the very serious threat posed by climate change. Alone among political parties, the Green Party has pushed at European, national and local level for a massive programme of energy conservation, alongside a whole range of renewable energy options."
"For this reason, the Green Party of England and Wales voted in March 2007 in favour of developing renewable energies in the Severn Estuary. But, at the same time, it rejected the proposals for a Severn Barrage - because the alternatives are far better."
"I wholeheartedly endorse our support for Stop the Barrage NOW in their campaign to avoid this inefficient use of public money, time and effort."
The government has said it will make a decision on whether or not to go ahead with the barrage by 2010.