The Green Party is to set out a plan for the UK’s rivers, as it calls for a “drastic change” to be made to water and sewage infrastructure.

Under its proposals, the party is pledging to nationalise water companies and invest £12 billion in infrastructure to prevent sewage being dumped into rivers and seas.

During a campaign visit to the River Wye, the Greens are also expected to urge the next government to increase funding to the Environment Agency to give it “teeth”.

On Wednesday, the party will test the River Wye for phosphate levels, alongside TV chef Hugh Fearnley-Whittingstall, as they call for a water protection zone around the river.

Between 72-74% of phosphate pollution in the Wye is caused by agriculture, according to Government figures. This can cause the death of many species that are vital to the river ecosystem.

Therefore, the Greens are pledging to triple support for farmers who want to transition to nature-friendly farming.

Ahead of the visit, the party’s candidate for North Herefordshire, Ellie Chowns said: “We are reminded of just how much this shared resource means to the community and why drastic change is needed.

“The decline in the Wye’s ecological status is a stark warning that has been ignored for too long. The river has no voice, but it does have a political manifesto that puts its priorities front and centre.

“We are here both to demand a water protection zone around the River Wye and to put forward a bold vision for how we can protect all of Britain’s rivers. We need to tackle sewage pollution through real investment in water infrastructure and putting people before profit by taking water companies back into public hands.

“And we need to tackle agricultural pollution through proper support for farmers to transition to nature-friendly farming, plus giving the Environment Agency the funding and teeth it needs to enforce the polluter pays principle. With these measures, we can restore our rivers back to health.”

Mr Fearnley-Whittingstall said: “Ellie and I are clear that the only way to end the scandal of our filthy water is to tackle the pollution at source.

“For the Wye this means addressing the factory farmed elephant in the room, and working closely with farmers to give them the support they need to grow food locally, and in a way that protects the environment.

“Nationally we need to be bold, and bring to an end the disastrous and unfair experiment with privatisation of a basic human right – clean water.