Campaigners trying to stop raw sewage being pumped into Lake Windermere, which is supposed to be a pristine monument to nature, are envious of Lake Annecy in France.

Volunteers testing the water quality of Windermere have found “really concerning” pollution in England’s largest and most famous lake. The analysis, in which 350 “citizen scientists” took samples of water at more than 100 locations around the lake, found “hotspots” of phosphorus, which causes algal blooms, and two types of bacteria that cause illness.

The Big Windermere Survey, involving 350 volunteers and over 1,000 water samples, has revealed consistently poor water quality across England’s largest lake. Concentrations of faecal bacteria in the lake were found to peak in summer but there were high levels throughout year.

Organisers of Kendal Calling have pledged to donate £100,000 to Lake District conservation projects over the next five years.

To kickstart the commitment, the music festival has donated £10,000 to Save Windermere.

A campaigner has accused a water firm and green regulator of “painting a fictitious picture” of Lake Windermere’s pollution. United Utilities (UU) previously claimed a 50% reduction in phosphorus discharges into England’s largest lake, in Cumbria, following investment between 2015 and 2020.

But Save Windermere founder Matt Staniek alleged this figure is based on “unverified assumptions rather than concrete data”. The Environment Agency (EA), in a blog post last year, said that phosphorus levels have declined by approximately 30% since 2020 – contradicting the claims made by the water company.

Nearly two hundred thousand litres of raw sewage was spilled in one day into a lake flowing into Windermere, according to campaigners who claim the discharge was illegal.

The details of the sewage dumping come as new legal rules take effect, requiring water firms to be more transparent about their efforts to stop pollution.

Campaigners are calling for regulators to urgently investigate whether water company United Utilities has been illegally spilling sewage into one of the UK’s most protected sites.

Before the election, during the election and after the election, the government promised us a complete root-and-branch review, a wide-ranging re-examination and a complete reset for the water industry. We were promised champagne but today we’ve been offered sour milk.

Ministers have been accused of misleading the public over claims that it has secured £100 billion in private investment for the water industry over the next five years.

Swimmers have been told to avoid part of a popular lake after harmful blue-green algae was found in the water. The blooms, which can make people ill if swallowed, were discovered at the Lakeside YMCA bathing area in Windermere, in the Lake District. Environmental campaigners said they believed it had been caused by a combination of pollution flowing into the lake and the warmer weather.

Water quality monitors near England's largest lake which were deemed ineffective by campaigners have now been moved.

The Environment Agency (EA) installed the monitors at Cunsey Beck, which feeds into Windermere in the Lake District, after a fish kill in June 2022 in which "100% of life" within the river was suspected to have died.

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.