Campaigners say analysis shows illegal sewage spills in Lake Windermere reach record levels

Sewage was illegally poured into the Lake District's famous Lake Windermere for a record number of days last year, campaigners say, citing new analysis.

They looked at official data released by United Utilities to identify times the water company had released untreated sewage into England's longest lake, when legally it should have been treating some of it.

The Save Windermere and Windrush Against Sewage Pollution (WASP) groups counted 140 days of what they deemed illegal spills in 2024 across six sites on the lake.

This was more than the previous record of 110 days in 2023, and higher than in any other of the three previous years, Professor Peter Hammond from WASP found.

United Utilities disputed the findings, saying some of the data was "erroneous" and that the method was different to that used by the regulator.

The company has earmarked £200m of investment to treat wastewater more thoroughly and stem the flow of the six overflow sites in question.

The news comes as water bills in England and Wales rise by an average of £10 per month. United Utilities customers are set to pay 23% more than they were.

Water companies are allowed to release untreated sewage into waterways when the network risks being overwhelmed, to avoid sewage backing up into people's homes.

The campaigners say United Utilities discharged sewage into the lake before that threshold had been breached. Other water companies in the country have faced similar accusations.

Last week, Environment Secretary Steve Reed said the amount of sewage being dumped into English rivers remained "disgraceful", despite some improvements.

Campaigners call for legal action

Matt Staniek, founder of Save Windermere, said: "What's happened in Windermere is clear: shareholder profits have been prioritised over the ecological health of one of our most iconic and culturally important landscapes.

"Bill-payers are being forced to cover the cost of a broken privatised system, yet even now, the proposed investment falls short of what's needed."

The group is calling for United Utilities to be prosecuted.

England's Lake District is designated a UNESCO World Heritage Site, based on the "universal value" of its scenic landscape that "everyone has a right to appreciate and enjoy".

But the landscape has turned bright green as algal blooms, fuelled by the nutrients in large sewage releases, swamp the waters, campaigners say.

United Utilities declined to provide more accurate figures when asked by Sky News, but said the campaigners had wrongly labelled spills at one of the sites, Ambleside, as illegal when the site had in fact complied with its permit.

A spokesperson said they were "extremely disappointed" that the campaigners "refused the opportunity to talk through the data so that they can get a better understanding of it".

"The methodology used by the campaigners is different to that used by the Environment Agency for its compliance assessments.

"On top of that, erroneous data has been used, tags and naming conventions in data sets appear to have been misunderstood, and assumptions seem to have been made on whether different types of flow meters have been installed.

"The methodology fails to use other corroborating information from the sites which would prove that spills did not occur. As a result, the numbers quoted are inaccurate."

"We're committed to playing our part in continuing to improve the water quality in Windermere."

It previously invested £75m to cut the amount of phosphorus entering the lake, which has cut the duration of such spills by 28% in the last year, they added.

(c) Sky News 2025: Campaigners say analysis shows illegal sewage spills in Lake Windermere reach record levels