BBC: Seven days of continuous sewage discharge recorded
Untreated sewage was continuously discharged into a Site of Special Scientific Interest for seven days.
Storm overflows at two water treatment plants in Cumbria have been discharging into sites that flow into Windermere since last Thursday, United Utilities figures show.
The water company said overflows are "designed to operate during heavy rainfall, like that seen in the Lake District over recent days".
Founder of the Save Windermere Campaign Matt Staniek said they are only supposed to occur in "exceptional circumstances" and disputed that recent weather conditions fell within that scope.
The wastewater treatment works at Near Sawrey began discharging into Cunsey Beck, which flows from Esthwaite Water to Windermere, at 06:11 BST last Thursday.
Similarly, Hawkshead Pumping Station started discharging at 03:27 BST last Thursday, which would have eventually flowed into Windermere via Cunsey Beck.
Water companies are allowed to release untreated sewage into rivers and seas when it rains heavily, to prevent homes being flooded.
Mr Staniek said: "Storm overflows are only supposed to occur in exceptional circumstances and, as far as I'm concerned, having been in Windermere since last Thursday I don't think we've had exceptional rainfall.
"Something like Storm Desmond put down exceptional amounts of rain.
"I just think that we've had a wet summer in the Lake District and that these sites should already have the capacity to deal with that."
Heavy rain fell in parts of Cumbria from about Wednesday last week, with Storm Lilian bringing more wet weather from Friday.
The Environment Agency said: "We understand the concern in the community regarding these discharges and we are working with United Utilities to ensure improvements are made in the next investment programme."
It had previously said rainfall does not override water companies' responsibility "to manage storm overflows in line with legal requirements".
A United Utilities spokesperson said it had invested "hundreds of millions of pounds in recent years to reduce the number of spills" and plans to invest more in the future.
