Campaigners are calling for increased testing after finding “deeply concerning” levels of bacteria in the sea following releases by Southern Water.

Volunteers from the Green Party and SOS Whitstable carried out citizen testing of water quality in popular bathing sites near the Swalecliffe treatment works outlet.

It comes as concerns about sea pollution continue to grow, amid the continued dumping of waste water into the sea.

Campaigners say the results revealed “very high” levels of E.coli - based on standards set by the Environment Agency - on two separate days after sewage releases.

The bacteria can cause diarrhoea, fever, cramps and vomiting - symptoms members of SOS Whitstable and other bathers say they have experienced.

One of the tests was carried out in West Beach on February 6, two days after a 2.4-hour waste water release. Another was taken in Tankerton on February 14, a day after a six-and-a-half hour release.

Meanwhile, volunteers say the tests showed bacterial pollution may have been at unsafe levels over 10 days, with intestinal enterococci being found in the water, which comes from faeces and is harmful to human health.

But the tests take into account all coliform bacteria - which are germs found in faeces - including a wider range of less harmful types.

Campaigners have called on Southern Water to fund more detailed testing to find out the composition of the pollution it is dumping into the sea.

Green Party councillor Clare Turnbull told how £500 had been spent on purchasing a better testing kit to be used at West Beach and Tankerton for 25 days from February 6.

But she says buying the kits is not sustainable and has called on the water company to carry out daily testing.

“It is shameful that Southern Water continues to pollute our seas,” she said.

“Our shellfish industry relies on clean sea water, as does our reputation as a beautiful seaside town for all to enjoy.”

She says she is “shocked” by the results, adding: “This is an indication that it is hazardous to health on some days if you swim.

“What we want is Southern Water to act more quickly to deal with the spillages.”

Dr Nick Mills, head of Southern Water’s storm water task force, says the firm fully supports citizen science and has offered electronic sampling equipment and scientific support to this and other groups.

“We completely agree [the online interactive map] Beachbuoy does not go far enough – near real-time 365-day information on storm releases is useful for recreational water users but the future lies in real time water quality testing,” he said.

“We are about to launch the UK’s first real time quality monitoring buoy off Hayling Island, Hampshire as part of a scientific programme to prove the technology can deliver usable data.

“The next buoy in this pilot will be off Tankerton Beach this summer. In the long run we hope Beachbuoy will show exactly what impact storm releases are having so we can target investment and partnership work.”

An Environment Agency (EA) spokesperson says it carries out bathing water sampling “according to strict protocols” - with analysis by an accredited laboratory and using quality-controlled processes.

“Sampling locations at designated bathing waters are also carefully selected to get the most representative sample of the E.coli present in the water,” they said.

“These are the accepted methods to assess bathing water quality across the UK.

“In addition, through the Storm Overflows Taskforce, water companies have agreed to make real-time data on sewage discharges available at bathing sites all year round.”

Between May 15 to the end of September, samples are collected by the EA from bathing water which is tested and the results are updated on its Swimfo website.