Anglian Water could be forced to pay millions in compensation after being named in a landmark legal case.

The water company is one of six firms facing legal action in a case which could see them ordered to pay more than £800m in compensation.

The case centres around allegations of underreporting pollution incidents and overcharging customers.

It comes after the company, which is £6.6m in debt, was identified as the worst-performing in the country for self-reporting incidents of pollution.

The case has been brought by Carolyn Roberts, an environmental professor who alleges companies have broken competition laws by misleading the Environment Agency and regulator Ofwat.

She said: "Like many others across the country, I have viewed with horror the escalating number of stories in the media regarding the volume of sewage discharged into our waterways and onto our beaches.

"It appears that because of the serial and serious underreporting at the heart of these claims, water companies have been avoiding being penalised by Ofwat.

"I believe this has resulted in consumers being unfairly overcharged for sewage services."

If the claims are successful, anybody who has paid a water bill to Anglian Water - or any of the five other companies - from April 2020 could be entitled to compensation.

A spokesman for Water UK, which represents companies like Anglian Water, said: "This highly speculative claim is entirely without merit.

"The regulator has confirmed that over 99pc of sewage works comply with their legal requirements.

"If companies fail to deliver on their commitments, then customer bills are already adjusted accordingly."

The case is the latest blow for the water provider, which has come under increasing scrutiny over sewage problems in recent months - including at Gorleston and Mundesley.

The other companies named in the case are Severn Trent Water, Thames Water, United Utilities, Yorkshire Water and Northumbrian Water.