Dave Shaw, who lives near Brecon, Powys, said he had “cherished memories” with his daughters of “pond dipping and looking in and around the water for wildlife”.

But the 56-year-old, who works as a wildlife educator, added that “some years ago, we started to notice a decline”.

“Rocks became coated in a brown sludge and the river began to smell – we no longer wanted our children in it,” he said.

Thomas Garland, 25, canoed the entire length of the Wye for charity in 2018.

“I grew up enjoying the benefits of the river, spending time throughout my childhood and adult years kayaking along it,” he said.

But having noticed “sludge on the banks” and less wildlife in recent years, he said he no longer felt comfortable in the water.

Law firm Leigh Day said it was acting on behalf of more than 2,000 individuals and businesses, bringing a class action lawsuit which would seek compensation for local people.

While it acknowledged the bulk of the pollution was due to “industrial-scale chicken production” it alleged sewage discharges “high in phosphorus and bacteria due to human faeces” were another contributing factor as they resulted in “odour, insect swarms, biodiversity loss and poor water quality”.