The water regulator is taking action against four more water companies, including Severn Trent and United Utilities, meaning every wastewater company in England and Wales is under investigation over sewage spills. Ofwat said it had served formal notices on Dŵr Cymru Welsh Water, Hafren Dyfrdwy, Severn Trent and United Utilities, asking them to provide evidence for its investigation into companies’ wastewater management in England and Wales. The regulator has looked at the companies’ environmental performance and data about how often they spill from storm overflows. It said this had heightened its “concerns that these companies may not be fulfilling their obligations to protect the environment and minimise pollution”. This means Ofwat is taking enforcement action against all 11 water and wastewater companies in England and Wales over sewage pollution. Once it has fully investigated, it will publish its findings and where appropriate take action over any breaches of legal obligations. Along with the Environment Agency, the regulator is investigating water companies over suspicions of widespread illegal sewage discharges across the network from thousands of treatment plants. The investigations have been going on for more than two years, with no findings published so far. In March, analysis of the latest data showed that more than 2,000 overflows owned by a number of companies were discharging raw sewage into rivers and seas. Ofwat’s investigations into Anglian Water, Northumbrian Water, South West Water, Thames Water, Wessex Water, and Yorkshire Water are ongoing. Southern Water remains subject to enforcement monitoring after a record £126m fine in 2019 over “shocking” failures at the company’s sewage treatment sites that polluted rivers and beaches in southern England. David Black, the Ofwat chief executive, said: “The fact that Ofwat now has enforcement cases with all 11 of the wastewater companies in England and Wales demonstrates how concerned we are about the sector’s environmental performance. “Where we find that companies have breached their obligations, we will continue to act – over recent years, we have imposed penalties and payments of over £300m on water and wastewater companies. “This is the largest and most complex investigation Ofwat has undertaken. However, Ofwat is committed to concluding these cases as quickly as possible, so that the sector can focus on delivering the £88bn expenditure the 2024 price review will unlock to deliver cleaner rivers and seas. “As part of this package of investment, £10bn is earmarked to tackle storm overflows with a target to reduce spills from storm overflows by 44%.” Severn Trent recently announced a programme to significantly reduce use of storm overflow, which Ofwat welcomed. Shares for Severn Trent and United Utilities, which are listed on the stock market, fell by about 4% and 3%, respectively, after the regulator’s announcement. Last week, Ofwat was criticised for letting water companies put up bills by an average 21%, or £94, over five years to fund improvements in environmental standards, at a time when customers have endured poor service, sewage dumping and leaks. This was described as a “bitter pill” by the new chancellor, Rachel Reeves. Campaigners for clean water, including the former Undertones singer Feargal Sharkey, argue that customers are in effect paying twice, and that they should not be paying for infrastructure investment that should have already been carried out to comply with companies’ operational permits. Severn Trent, United Utilities and Hafren Dyfrdwy said they would work “constructively” with Ofwat. A spokesperson for Dŵr Cymru Welsh Water issued a similar statement, saying: “We have been working closely with our regulators on the monitoring of our wastewater treatment works and are investing at record levels to improve service.”