Tonnes of raw sewage were dumped into the sea yesterday by Southern Water after the company’s pumps became blocked.

The firm blamed a “technical error” at its treatment works in Western Road, Worthing, for causing untreated effluent to be pumped into the sea for at least 14 hours.

Action group Surfers Against Sewage said the dumping could lead to a raft of “disgusting” diseases.

The Environment Agency said that it was investigating the malfunction.

Southern Water said a build-up of non-biodegradable waste meant its pumps had become blocked late on Saturday night.

It said in order to prevent the backing up and flooding of nearby properties it diverted the waste more than three miles out to sea.

Southern Water tankers were brought in yesterday to try to reduce the amount of raw sewage going into the water.

The company and the Environment Agency were working with Worthing Borough Council to make the public aware of the danger, by using red flags on the beach.

The Environment Agency said it could not rule out waste being washed up along the shore.

Gareth Bates, from the agency, said: “We will remain onsite to ensure that all action is taken to prevent further risk to the beach and coastal area and we will oversee the clean-up operation.

“A full investigation into the incident is currently underway as well as all our efforts being focused on reducing the risk of pollution to the coastal area.”

A Southern Water spokesman added: “We can reassure customers that we are doing everything we can to minimise the impact of this incident and to get the site back online as soon as possible.”

Andy Cummins, the campaign director at Surfers Against Sewage, said if Southern Water was found to be at fault he would like to see the company prosecuted.

He added: “The associated health risks are severe and extremely long.

“Warning people is paramount as it can lead to disgusting diseases such as hepatitis A, meningitis and gastroenteritis.”

Mr Cummins said while Southern Water screened the waste for larger sanitary items it would not remove the pathogens in the sewage.

But he added that the public should also take responsibility for flushing sanitary waste down the toilet rather than correctly disposing it in bins.