Sewage discharged into coastal waters ruins one in six swimming days at Britain’s beaches, data shows.

Clean water campaign group Surfers Against Sewage found that water companies dumped untreated sewage in Britain’s seas and waterways 5,517 times over the year to September, an 88 per cent rise on last year’s figure of 2,941.

During the official bathing season between May 15 and September 30, 16 per cent of swimming days were rendered unsafe, the charity said.

Some 3,328 were issued during the summer bathing season, up on 2020’s figure of 1,195. Some of the increase is due to more data being provided by water firms, which have agreed to be more transparent with their data following public outrage at the practice.

Untreated sewage is discharged from Britain’s dated waste systems into rivers and seas when they become too full because of rain. This is supposed to happen only in exceptional circumstances following wet weather, but data shows it now takes place routinely.

The group said its analysis also showed sewage regularly being dumped outside periods of heavy rainfall. Six of eight rivers it analysed over the summer were also regularly contaminated with dangerous levels of e-coli, it said.

‘Urgent need for action to protect and enhance our rivers and seas’

Hugo Tagholm, the chief executive of Surfers Against Sewage, said: “The internationally recognised guidance is that you shouldn’t really go in sewage polluted water for up to 48 hours after a sewage event, and that would include from sewer overflows here in the UK.

“Sewage carries all sorts of bacteria and sort of pathogens with it. People can pick up stomach and ear and eye and nose infections. We have dozens of reports every year, and that’s just the tip of the iceberg.”

A clause in the recently passed Environment Act placed a “duty” on water companies to reduce the impact of the discharges.

However, there are questions over whether it is sufficiently enforceable, amid disagreements over where the money for the upgrades should come from.

A spokesman for industry group Water UK said: “Water companies recognise the urgent need for action to protect and enhance our rivers and seas.

“We know we need to go further and water companies want to invest more to improve infrastructure and stop harm from storm overflows and outfalls.

“With our coastal bathing waters we have a good base to build on, with more than 70 per cent rated as ‘excellent’ and over 90 per cent as either ‘excellent’ or ‘good’.

“This improvement has come about thanks to collaborative working between industry, government, regulators and other stakeholders over several years.”