Southern Water Services have been hit with a staggering £500,000 fine after untreated sewage was discharged at Swalecliffe Brook last year.

Judge Adele Williams ruled the company had been negligent for the incident which happened as Whitstable prepared for its annual oyster festival.

Canterbury Crown Court heard that a 1.2 kilometre stretch of water was so polluted that eels were spotted trying to jump out of the brown water.

Two of the company's pumps had stopped working triggering two alarms which weren't acted upon.

SWS blamed the failure on one of its workers – but Judge Williams said she didn’t accept that and criticised the management.

She said the water company had "displayed some complacency" in failing to respond promptly to problems before the incident in July last year.

The sewage leak was reported by a passer-by who spotted the brook "black and smelling of sewage" near to the sea.

A local festival supplier was forced to obtain oysters from other areas after fears over contamination.

SWS later admitted breaching regulations because of an undue delay" in tackling the problem, causing "the prolonging of the incident".

Prosecutor Richard Banwell told the court: "The water was discoloured and had a distinct sewage odour. Dead sticklebacks and eels could be seen. Test results of the water confirmed the brook had been subject to significant organic pollution."

The court heard that a brown trout, 93 sticklebacks, a goldfish and 155 eels, which are critically endangered species, had died.

After the alert, Canterbury City Council immediately put up warning signs alerting the public to the problem along one of Kent’s moist popular beaches.

Mr Banwell said the area is popular for the harvesting of oysters and tests later showed there were “higher levels of E coli than would have been expected at that time of year”.

Seasalter Shellfish had stopped harvesting the day after the incident and the owners of West Whelks, one of only two suppliers to the annual oyster festival, said it would not take any of the oysters to the festival “due to the risk of contamination.”

"The water was discoloured and had a distinct sewage odour. Test results of the water confirmed the brook had been subject to significant organic pollution..." - Prosecutor Richard Banwell

Mr Banwell added: “Last year would have been the first time in a few years that the festival would have been supplied by a majority of local oysters rather than those harvested outside Whitstable.”

In the end, West Whelks obtained oysters from elsewhere and sold 35,000 of them during the festival week.”

After the hearing SWS’ CEO Matthew Wright said he was surprised by the size of the fine and said its lawyers were looking at the possibility of an appeal.

He added: “I don’t accept the criticism of the company’s management and we take every single incident very seriously indeed.”

Mr Wright added that SWS was spending £1.7m on improvements but added: “We are doing our best but we can never rule out another incident happening.”

Alan Cansdale, environment manager at the Environment Agency, said: “Southern Water has acknowledged that they had sufficient warning and knowledge of the incident to minimise the impact on the local environment, but failed to act swiftly and notify partners to help this happen.

"This incident, and the scale of the subsequent environmental impact, was a result of inadequate urgency to recognise there was a problem at the site."

Canterbury City Council’s Environmental Health Officer, Sarah Maloney, added: “We were pleased to be able to work in partnership with the Environment Agency in this case.

"The good reputation of our shellfish industry is very important to local businesses and the council.

"We work hard all year to ensure our residents and visitors are able to enjoy local shellfish safely, so it’s vital we can respond to pollution events such as this promptly and effectively."