Campaigners have taken the Government to court over an alleged failure to stop farmers from polluting the river Wye.
Anti-pollution charity River Action took the Environment Agency (EA) to court on Wednesday for a judicial review, claiming it is allowing destructive levels of nutrients from chicken manure to enter the river.
The Wye is the fourth longest river in Britain and partly forms the border between England and Wales as it runs from central Wales to the Severn estuary.
It is estimated that about 20 million chickens are raised in the Wye catchment area at any one time – about 25% of UK poultry production.
A large amount of organic manure has been spread over the area leading to a substantial increase in levels of phosphorus in the soil.
When washed into the river by rainwater, the phosphorus causes prolonged algal blooms which turn the water an opaque green.
River Action campaigners gathered outside the Civil Justice Centre in Cardiff, displaying banners and banging drums, demanding that the Environment Agency step up to stop the spread of excess nutrients.
They were joined by Feargal Sharkey, the pop star turned water quality campaigner.
He said: “The simple truth of the matter is that every river in England is dying.
“Every special area of conservation, every site of special scientific interest is failing. The system is failing to protect them.
“How far are we going to allow large companies to exploit the environment to their benefit and not necessarily ours?”
Explaining how he got involved in River Action, he said: “I wanted to go fishing and the river I wanted to fish in was in a bad shape.
“I wanted to do something about it, I wanted to scratch that itch. And every time I scratched that itch I got a bigger itch.
“I see a lack of political oversight of the laws that were created to protect the environment and that has to stop.
“We hope the court will agree with our assessment that the EA and Defra (the Department for Environment, Food & Rural Affairs) have failed to apply the law the way it has been written.
“(The river Wye) should be one of the most protected in Europe and yet it is failing, people can now see algae blooms, clear toxicity of the river.
“This is not something happening in some far off country on the other side of the planet, it is happening here and the Government agencies set up to protect it are allowing it to be destroyed.”
Charles Watson, the chairman and founder of River Action, said the status of river had already been downgraded and without protection the only way it could go is it becoming a “dead river”.
“It’s frequently voted Britain’s favourite river and it’s been allowed to go into a death spiral,” he said.
“The very bodies that are supposed to support it have failed.
“This is our last line of defence, the court is the place we can go to try to save our rivers. People are desperately concerned about this.
“Anywhere else in Europe someone would be locked up in prison for what is happening here.”