Southern Water has been branded the worst water company in the country for its environmental performance.

It comes after the firm was hit with a record £90 million fine last week for dumping colossal amounts of raw sewage into the sea for years.

The company unleashed up to 21 billion litres into protected waters - the equivalent of more than 700 Olympic swimming pools - with flagrant disregard to the law.

A report published today by the Environment Agency said the performance of Southern Water has given them "serious cause for concern".

The research looked at the performances of the nine water and sewerage companies across England, which is measured using the Environmental Performance Assessment (EPA) using a star system.

Companies are analysed based on reducing pollution incidents and increasing reporting of them, complying with discharge permits, completing environmental improvement schemes and providing secure supplies of water.

Southern Water was at the bottom of the table of 2020's results alongside South West Water - each being slapped with two stars.

In comparison, for the first time more than half the sector has achieved the highest rating - the industry leading status, four stars.

Wessex Water, United Utilities and Severn Trent Water have sustained "industry leading performance" for most of the five year period of the EPA.

Northumbrian and Yorkshire Water have also shown improvements based on a range of measures including pollution incidents and compliance with permits.

The report states: "Southern Water and South West Water’s performance has been consistently unacceptable.

"The remaining companies have failed to make any significant progress to achieve and maintain leading performance. We will continue to push improvements across the sector."

Southern Water was sentenced on Friday at Canterbury Crown Court after admitting 6,971 illegal discharges from treatment works in Kent, West Sussex and Hampshire from 2010 to 2015.

While effluent destroyed whole oyster beds in the Swale and Solent rivers, with fishing businesses suffering, board members were aware of the huge scale of the illegal operation, the court heard.

The firm’s lawyers argued the sewage was discharged following “negligence” rather than a “deliberate” act to reap “considerable financial advantage”.

It dumped sewage into The Swale affecting Sheppey, Whitstable and Herne Bay, where waters are protected to help maintain the ecosystem.

Raw sewage was also spilled into The Solent’s protected waters, between Southampton and Chichister.

Shellfish in both rivers were made unfit for human consumption and withdrawn from the market, but it is believed 9,000 to 10,000 entered the human food chain, the court heards.

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