Prolonged high temperatures have seen harmful algae blooms spread across the "entirety" of England's largest lake, a campaigner has warned.

Council leaders have urged swimmers and dog-walkers to stay out of Lake Windermere because of the potentially toxic algae covering the water's surface - after experts warned that fish in the lake are choking to death and rivers and canals across 'Tinderbox Britain' turned green during the heatwave.

Windermere is dying and people swimming in it have been exposed to potentially toxic algal blooms, according to one passionate eco campaigner.

Lake Windermere, in Cumbria, has turned green because of toxic algae blooms worsened by last week’s heatwave. Local resident Matt Staniek’s petition to save Windermere from “sewage and an environmental catastrophe” has amassed over 130,000 signatures.

British rivers and lakes are being choked with algae thanks to the record-breaking heatwave that has scorched the UK.

Visitors to Windermere have been urged not to swim after sightings of large blooms of potentially dangerous blue-green algae in England’s largest lake.

“Some of our best loved and most iconic wildlife face a perilous future. We must act now to ensure that generations to come can marvel in the joys that our freshwater habitats can provide, from the magical sight of otters playing in our streams, the vibrant blue flash of kingfishers in flight, and the epic migration of the Atlantic salmon,” said a joint appeal by all of Britain’s major conservation organisations published last September.

A zoologist who is campaigning to prevent sewage being dumped in Lake Windemere has warned of an impeding environmental disaster after claiming his beloved dog fell seriously ill while swimming in England's largest lake.

A sewage dump was responsible for the deaths of hundreds of salmon, trout and pike in a stream leading to Windermere, a study suggests.

England’s largest lake is at risk of “ecological destruction” due to pollution from sewage works, agriculture and nearly 2,000 private septic tanks, a conservationist has said.

England's largest lake is on the verge of "catastrophe" unless urgent action is taken to improve its water quality, a conservationist has warned.

Matt was filmed for Countryfile as part of a wider piece on water companies not reporting sewage spills nationally, with the focus being on our largest lake.