Thousands of people have taken part in protests at beaches, rivers and lakes across the UK amid a row over the state of the country’s waters.

The demonstrations follow reports that millions of litres of raw sewage were pumped into Windermere in the Lake District for 10 hours in February.

The situation was labelled a “scandal” by opposition politicians, while Downing Street said it was “completely unacceptable” and the Environment Agency had the power to launch a criminal prosecution if necessary.

On Saturday, protesters gathered at swimming spots across the country to call for an end to sewage discharges into all bathing and high-priority nature sites by 2030.

The campaign, co-ordinated by Surfers Against Sewage (SAS), saw protests at more than 30 locations, from West Pier in Brighton to Gyllyngvase Beach in Falmouth.

In Brighton, Olympic gold medal runner and keen paddle-boarder Dame Kelly Holmes addressed demonstrators through a megaphone before leading dozens in a paddle-out.

In Falmouth, surfers paddled out en-masse while sea-kayakers carried placards on their boats calling for fish not faeces.

Meanwhile, more than 200 people entered the water at a wild swimming spot at Ferris Meadow Lake in Surrey.

Emma Jackson, who organised the Shepperton Open Water Swim event, said she was contacted by SAS after setting up a campaign to save the lake from the River Thames Scheme, which will build a new flood relief channel through the area.

She said the lake naturally cleans itself and was much safer to swim in than the Thames but, under the proposal, the lake would be connected to the river, leaving it in danger of contamination.

She said she could not imagine being unable to swim at the lake if it became unsafe. adding: “I don’t want to think about it”.

“Today is the first day of the season here at Shepperton Open Water Swim and I can tell you, speaking to my community of swimmers, they are all just over the moon to be back and it is a really special place for us.

“There are plenty of spaces you can swim, there are other lakes in the local area, there are other bodies of water that are equally as safe and we can we can swim in but… this place holds a special place in a lot of people’s hearts.”

Dinah Sershi, 54, and Georgina Palffy, 55, who are regular swimmers at the lake, attended the protest.

Ms Palffy said they would feel “bereft” if they were no longer able to swim there due to water contamination.

“We do swim in other places, but none of them are quite as magical as this, and none of them have the amazing clean water that they get here, which is something really special,” she said.

Ms Sershi said swimming at the lake was particularly important for women who are going through the menopause.

“I’m particularly passionate about swimming here,” she said.

“I’m a woman in my 50s. And I know a lot of people in this community are in their 40s and 50s and find the water an incredible way of managing the menopause symptoms.”

Emma Pattinson, 55, whose family operates Shepperton Open Water Swim, said there was an “alternative route” for the River Thames Scheme, which would circumvent the lake.

“Obviously we don’t want anyone to be flooded on our behalf,” she said.

“But we also want this lake to retain its clean water for our swimmers.

“It matters a lot to them.”