Thames Water and two other water firms handed record fine
Oxfordshire's water company alone has been fined £104 million.
Ofwat has proposed £168 million of fines for three of England's biggest water companies for failing to manage sewage spills, including a £104 million penalty for Thames Water.
The water regulator proposed the fine for Thames, as well as a £47 million penalty for Yorkshire Water and £17 million for Northumbrian Water, as the first batch of results from its biggest ever investigation into the industry.
The penalties relate to water firms' management of their wastewater treatment and sewer systems, which have come under heavy criticism for releasing too much pollution into rivers.
In an announcement on Tuesday morning, Ofwat said the firms "failed to ensure that discharges of untreated wastewater from storm overflows occur only in exceptional circumstances, which has resulted in harm to the environment and their customers".
It added that there was a "strong correlation" between high spill levels and operational issues at their wastewater treatment sites, "which points to these companies not having properly operated and maintained their wastewater treatment works".
It said the firms had failed to upgrade their assets where necessary, and had been slow to grasp their obligations to limit pollution from storm overflows.
Ofwat chief executive David Black said: "Ofwat has uncovered a catalogue of failure by Thames Water, Yorkshire Water and Northumbrian Water in how they ran their sewage works, and this resulted in excessive spills from storm overflows.
"Our investigation has shown how they routinely released sewage into our rivers and seas, rather than ensuring that this only happens in exceptional circumstances as the law intends.
"The level of penalties we intend to impose signals both the severity of the failings and our determination to take action to ensure water companies do more to deliver cleaner rivers and seas.
"These companies need to move at pace to put things right and meet their obligations to protect customers and the environment. They also need to transform how they look after the environment and to focus on doing better in the future.
"Looking to the future, we want transform companies' performance under our new price control that starts in April next year, so we reduce spills from sewage overflows by 44% by 2030 compared to 2021 levels."