TESCO has been warned by environmentalists not to allow itself to “potentially contribute to the destruction” of the River Wye by procuring its products from the firms responsible.

Campaigners say the supermarket giant is the biggest customer of egg producer Noble Foods and chicken producer Avara Foods, which are responsible for a large share of the 20 million chickens farmed in the Wye catchment.

And the company was forced to defend its role in protecting the Wye recently after campaign group River Action sent a letter to senior Tesco figures calling for action.

The group says Tesco is key to saving the river from irreparable ecological harm, caused by high amounts of phosphate from chicken manure washing into it.

Phosphates cause algal blooms in the river which can turn the river a soupy green, starve it of oxygen and cause loss of river wildlife.

Represented by law firm Leigh Day, the letter warns: “If this situation continues to be left unaddressed, the river Wye faces ecological collapse.”

It calls on the retailer to meet the LEAF Marque environmental standard in its poultry supply chain and publish environmental risk assessments to insist that suppliers have an approved manure management plan.

River Action founder and chair Charles Watson said: “Tesco must not allow itself to potentially contribute to the destruction of one of the nation’s favourite rivers by continuing to procure its poultry products without requiring major environmental improvements from suppliers.”

A Tesco spokesperson responded: “We want to play our part in ensuring the protection of the river Wye, alongside other actors across the food industry.

“Together with our partners WWF, we have directly funded the Wye & Usk Foundation, which works with our suppliers on implementing nature-based solutions, including tree planting, as well as supporting farmers to test soils and implement on-farm best practice that all help reduce pollution in the River Wye.

“We have encouraged all of our suppliers to sign up to the Water Roadmap, which looks to reduce water pollution in key sourcing regions including the Wye and Usk catchment.”

Noble Foods produces grain at Clearwell Mill in the Forest to feed poultry at intensive units (IPUs) across Gloucestershire, Herefordshire and Shropshire.

The company has come under fire for its adverse impact on the Wye - as well as ancient woodlands in the Forest of Dean - in recent years, with locals protesting at the gates of Clearwell Mill against its operations back in March.