Severn Trent faces paying out millions in legal action on pollution data – but 'strongly refutes' claims

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

But Severn Trent has hit back at the developments, describing the case as "a highly speculative claim with no merit which we strongly refute".

The firm also said it is "wholly and completely wrong" to suggest it has misled regulators, adding that all of its pollution data is checked by the Environment Agency.

The case, led by Professor Carolyn Roberts, an environmental and water consultant who is represented by Leigh Day Solicitors, claims that water companies have broken competition laws by misleading the Environment Agency and the regulator Ofwat.

She alleges they have been underreporting the number of sewage discharges, resulting in customers being "unfairly overcharged" for waste water services, and that had sewage discharge reporting been accurate it would have lowered customer bills.

The first claim, brought on behalf of eight million people against Severn Trent Water, is estimated to be worth more than £330 million.