A huge legal claim is being made against one of Herefordshire’s largest firms over pollution in the river Wye.

It is alleged that poultry producer Avara Foods is responsible for damage to the river and its tributaries which it should clean up, as well as paying “hundreds of millions of pounds” to people and businesses impacted by it, according to law firm Leigh Day which is bringing the civil claim.

The river Wye area is now thought to house at least 23 million birds at any one time, around four-fifths of which are processed by Avara, a major supplier to Tesco.

This gives rise to large amounts of phosphorus-rich manure which can leach into the soil and into the river if spread on fields as a fertiliser, causing lethal “blooms” of algae.

Avara says it no longer sells poultry manure to farms in the area, but ships it out to other parts of the country instead, as part of a longer-term plan to address the issue.

Leigh Day claims that Avara’s “industrial-scale chicken farming has been the overwhelming cause of phosphorus pollution which is damaging the river”.

Those who live around the river Wye across a wide area of Herefordshire, Monmouthshire and Powys – potentially tens of thousands of people – can still join the legal claim for “private and public nuisance”, Leigh Day says.

As well as property owners, this could include swimmers, canoeists, walkers, anglers, clubs and leisure businesses who could also have been affected by nuisance from living near chicken farms, such as smells, insects and noise.

Among claimants is Hereford resident Peter Redding, 55, a keen “coracler” who used to paddle his ancient craft on the river after work to benefit his mental health.

“But now I find I get off the river angry,” he said. “Rather than seeing sparkling pebbles under the water, all we see now is grey sludge. Now if I see kids on the river I tell them to get off.”

Leigh Day is also pursuing separate legal action on behalf of campaign group River Action against the Environment Agency, claiming it failed to enforce its own rules regarding run-off from farms in the Wye area.