SIX private water companies across England are facing landmark legal action over allegations of under-reporting pollution incidents and overcharging customers.

Severn Trent Water, Thames Water, United Utilities, Anglian Water, Yorkshire Water and Northumbrian Water could end up forking out more than £800 million in compensation to over 20 million customers if the cases are successful.

Environmental and water consultant Professor Carolyn Roberts, who is being represented by Leigh Day Solicitors, claimed that the firms have broken competition laws by misleading the Environment Agency and regulator Ofwat.

She alleges they have been under-reporting the number of sewage discharges, resulting in customers being “unfairly overcharged” for wastewater services, and that had sewage discharge reporting been accurate it would have lowered customer bills.

Prof Roberts 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 on to our beaches.

“The population has a right to expect that our rivers, lakes and seas will generally be clean, except under exceptional circumstances.

“It appears that because of the serial and serious under-reporting at the heart of these claims, water companies have avoided being penalised — I believe this has resulted in consumers being unfairly overcharged for sewage services.”

Anyone who has paid a water bill to one or more of these companies from April 2020 — or April 2017 for Severn Trent Water customers — may be entitled to compensation if the claims succeed. 

Leigh Day, which said the move is the first environmental collective action case of its kind, is seeking money for customers on an opt-out basis, meaning people only have to come forward to claim compensation if the case is successful.

It is bringing Severn Trent Water to a competition appeal tribunal and will issue five further claims against the other water companies over the coming months.

Leigh Day partner Zoe Mernick-Levene hailed the “hugely significant” claims.

“Not only is compensation being sought for millions of customers who have and continue to pay higher water bills, but we hope that it will also send a message to water companies that they cannot unlawfully pollute waterways and mislead their regulators without consequence.”