Raw sewage has been repeatedly dumped illegally into one of England’s most famous lakes over a three-year period.

Water company United Utilities failed to report most of the 140 million litres of waste which was pumped into Windermere between 2021 and 2023, the BBC revealed.

United Utilities claims it self-reports “over 94% of potential pollution incidents to the Environment Agency” yet some of the releases were “potentially non-compliant”.

The water company’s illegal sewage activities went on for far longer than previously known, also revealed to be far more extensive.

United Utilities illegally pumped sewage into Windermere for 165 hours, of which at least 118 hours were not reported to the environmental regulator.

Founder of Save Windermere and campaigner against sewage pollution, Matt Staniek, said Windermere was “the jewel in the crown of the Lake District National Park, and it’s being used as an open sewer”.

Back in January this year, United Utilities reported some discharges into the lake from October 2023 onwards.

However, the BBC obtained the company’s operation data dating back to January 2021 which shockingly shows the illegal sewage releases had been taking place for over three years.

This is far longer than the four months United Utilities retrospectively reported.

Releasing sewage into rivers and lakes is sometimes necessary to prevent the wastewater system from being backlogged with heavy rainfall. However it can cause damage to the environment creating algal blooms and can even kill fish.

The information obtained showed Glebe Road pumping station’s involvement in Bowness-on-Windermere. Thi is the only site which discharges directly into the lake, designed to pump wastewater from the local area to the nearby sewage works for treatment.

As long as the pumping station releases at least 245 litres of sewage a second to the treatment works, it is authorised by the Environment Agency to discharge raw sewage into the lake when it rains.

This key condition is supposed to protect Windermere, ensuring that even in wet weather, most sewage is sent for treatment.

Failing to comply with the permit is a criminal offence.

The BBC found the station had failed to comply with the permit by discharging sewage into the lake at times when it had not been pumping the required amount for treatment.

The water company declined to provide the the data showing exactly when each of the pumps into the lake was operating, claiming this data is classed as “internal communications”, which did not have to be disclosed under environmental information regulations.