Campaigners say a report highlighting a North Yorkshire river as one of the most polluted in the country strengthens the need for "political action".

The Angling Trust study found the River Swale to be among the country's most contaminated waterways.

Anglers around the UK have been testing the water quality of rivers in their catchments. In December 2023, there were 641 anglers from 240 angling clubs actively monitoring pollution on 190 rivers.

Their annual report finds that of the 163 rivers which were regularly sampled (more than five times), 83 per cent failed to meet the phosphate standard for a good ecological status in at least one sample.

The River Swale was one of the waterways with the highest phosphate averages.

The main sources of phosphorus in rivers are sewage effluent and losses from agricultural land.

Among the other rivers highlighted as having "the highest phosphate site averages" were the Ure, Nidd, and Upper Ouse.

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Ron Wood, development officer of the Richmond Angling Society, said: "These findings underscore the urgent need for political action. Therefore, the Angling Trust is calling on all political parties to include clear, actionable plans in their general election manifestos to tackle river pollution and to strengthen and enforce environmental protection laws.

"I am chairman of two local angling clubs, Gilling West Fly Fishers and Richmond and District Angling Society.

"Both clubs are actively involved in the Angling Trust 'Anglers Against Pollution' campaign and carry out water quality testing on a monthly basis.

"We are deeply concerned about the poor state of our local rivers and the effect it is having on the fish stocks, birds and wildlife. It is vitally important that we have clean rivers."

Hilary Plews, a member of the Save Our Swale group, said: "We are so grateful that these results have been published.

"In the testing we have been carrying out, which is not as in depth yet, we have also been seeing high levels.

"This is not a one off. There is a real problem with phosphates in the Swale.

"We are waiting for a letter of support from Rishi Sunak to help us push for bathing water status.

"In the next few months we hope to be publishing our findings as well."

Jamie Cook, Angling Trust CEO, said: "The Angling Trust's Water Quality Monitoring Network (WQMN) initiative harnesses the passion our members have for rivers and enables them with tools and training to create a rapidly expanding community of citizen scientists who monitor, understand, and actively contribute to the preservation of their local rivers.

"Due to regulatory failures, it often falls to the Angling Trust's sister organisation, Fish Legal, to take legal action against polluters on behalf of anglers.

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"The first annual WQMN report proves that across the country rivers are suffering from too much phosphate which is extremely damaging in freshwater.

"We need to see much more enforcement and an update of existing laws to tackle the scourge of river pollution and hold polluters to account."

An Environment Agency spokesperson said: “We take our responsibility to protect the environment very seriously and will always pursue and prosecute those that cause deliberate harm to the environment. In 2023, we accepted the largest ever Enforcement Undertaking of £1m by pursuing enforcement action against Yorkshire Water for unauthorised sewage discharges.

“The EA carries out around 90,000 water quality sampling visits a year from 13,000 different locations so we can see what is happening in England’s waters. Our data is available publicly online. Our monitoring currently indicates that the seven main water bodies that form part of the River Swale Catchment all achieve either good or high status for Phosphate.

“We continue to strengthen our regulation by expanding our specialised workforce, increasing compliance checks and using new data and intelligence tools to inform our work.”