BBC: All water firms now investigated for sewage spills
All 11 water and wastewater companies in England and Wales are now under scrutiny over sewage spills, after the regulator said it was expanding its investigation.
On Tuesday, Ofwat opened enforcement cases into four more firms - Dŵr Cymru Welsh Water, Hafren Dyfrdwy, Severn Trent and United Utilities - as part of its probe into how companies manage their sewage treatment works and networks.
It began its investigation in 2021 and if found in breach the companies face being fined.
Ofwat chief executive David Black said the latest move showed "how concerned we are about the sector's environmental performance".
It comes a week after water firms hit back at Ofwat's proposal of a £19-a-year rise in bills to tackle problems including sewage leaks, with the companies saying the increase would not be enough.
Water suppliers have faced increased scrutiny over their environmental and financial performance, as well as executive bonuses and pay.
In May, the BBC found that millions of litres of raw sewage were illegally pumped into one of England's most famous lakes, Windermere in the Lake District, after a fault, and that United Utilities failed to stop what was found to be illegal pollution.
Every major English water company has reported data suggesting they have discharged raw sewage when the weather is dry - a practice which is potentially illegal.
Water companies can release untreated sewage into rivers and seas when it rains to prevent it flooding homes, but such spills are illegal when it is dry.
Announcing the four firms facing new enforcement action, Ofwat said its investigation had highlighted its "concerns that these companies may not be fulfilling their obligations to protect the environment and minimise pollution".
