The River Itchen has been branded a "public health hazard" by a conservation group as it warned people not to go into the water due to high levels of E. coli.

The Friends of the Itchen Estuary spoke out about the state of the river as the Environment Agency revealed Southern Water was responsible for 317,285 hours of sewage spills last year.

The new figure is more than double the 146,819 hours of spillages from storm overflows in 2022, with an average duration of 10.8 hours for each spill compared to 8.8 the year before. 

But now, Friends of the Itchen Estuary chairman Gavin Millar has warned that 48 samples taken by his group and analysed in a lab found E. coli levels more than ten times higher than a "satisfactory" level.

He says storm overflows are not to blame, but the "six Olympic swimming pools worth of poorly treated sewage effluent" from Portswood Sewage Works were.

READ MORE: Sewage spills from storm overflows in 2023, by water company

He added: "In other words, sewage levels in the Itchen Estuary are a public health hazard for swimmers, and for other water contact sports such as paddle boarding, kayaking, and sailing where participants may come into close contact with estuary water."

Southern Water previously outlined plans to designate the River Itchen at Riverside Park as an inland bathing water site. 

But Gavin said the E. coli levels meant an Environment Agency bathing water quality categorisation of "Poor" for with swimming "not advised". 

Samples were taken from under Cobden Bridge, Northam Bridge, the Itchen Bridge and opposite Dockhead with sewage emerging from opposite Riverside Park.

It comes as Southern Water has been slammed after data released on Wednesday showed there were 29,494 spills from monitored storm overflows in 2023, compared with 16,688 the year before.

The average number of spills per monitored storm overflow was 30.7, almost double the 17.8 in 2022. 

Director for Wastewater Operations at Southern Water, John Penicud, said slashing the number of storm releases is a "top priority".

"Last November we announced our £1.5 billion storm overflow reduction plan which will combine innovative engineering with nature-based solutions.

"The past 18 months have been the rainiest since records began. The ground is utterly waterlogged in many areas, inundating our own sewers and customers’ drains and sewers. 

"We’re extensively relining sewers, to keep sewage in and rainwater out, and our storm release reduction pilot schemes have already proved that nature-based systems can have a real impact.”

A spokesperson added that last year was the sixth wettest on record since 1836 adding that more than £70m is being invested at the wastewater treatment works at Millbrook, Woolston, Ashlett Creek to improve water quality.

READ MORE: Southampton homes left without water for urgent works

Southampton Itchen MP, Royston Smith told the Echo: “No one wants outflows into our rivers but we must acknowledge the facts.

"The comparison with 2022 is not reliable. 2023 was the 6th wettest year since records began and 2022 was the 8th driest.

"Rainfall is the primary driver of outflows. Currently, and there are dozens of upgrades being delivered across the country, heavy rain overwhelms our Victorian sewage system.

"If all outflows were stopped dirty water (not raw sewage) would run down our streets and likely come up through our toilets.

"Water companies face record fines if they don’t stop outflows and are investing billions to upgrade our ageing sewage and water systems.”   

But Lib Dem parliamentary candidate for Eastleigh, Liz Jarvis said: "It is a complete scandal that Southern Water is continuing to pump filthy sewage into our rivers and waterways, and yet the Government has consistently failed to hold them to account."