A fresh attempt to change the law to stop water companies from releasing raw sewage into rivers has been launched by a senior Conservative MP. Philip Dunne, the chair of the environmental audit committee, is seeking in a private member’s bill to place a duty on water companies to ensure untreated sewage is not discharged into rivers and inland waterways. The attempt to force water companies to act comes after data obtained by the Guardian revealed nine English water and sewerage companies released untreated sewage into rivers more than 200,000 times last year. The spills of human excrement mixed with rainwater via storm overflows into rivers lasted for a total of 1.53m hours, the data reveals. The spills are permitted in extreme circumstances, such as torrential rainfall, when the sewerage system cannot cope with the amount of liquid and discharges and are made to release pressure to stop sewage backing up into people’s homes. But the data reveals what critics say is the frequent discharging of sewage and raises public health concerns as increasing numbers of people use rivers to swim, kayak and paddleboard. In 2017-18, more than 4 million people swam in open water, including rivers and lakes, according to the Outdoor Swimming Society. Dunne’s bill is being drafted to submit to parliament in the autumn. It will attempt to crack down on the practice of releasing untreated sewage from combined sewer overflows (CSOs). “There is a disconnect between the requirements of water companies to take responsibility for monitoring and reporting on overflow discharges and what they are actually doing,” he said. Dunne told the environment secretary, George Eustice, at a hearing last week that it was time for “water companies to be introduced to the concept of ‘the polluter pays’”. He said firms were failing to monitor their discharges and categorise them as standard or substandard as they were required to. “I raised concern that water companies were not classifying their spills and this voluntary approach is not being enforced by the Environment Agency or [the water regulator] Ofwat,” Dunne said. “It is clear this must be addressed and the regulations enforced before the condition of waterways is compromised further. “Not one single water company has done comprehensive classification of their CSO discharges.” The MP for Ludlow, in Shropshire, said the companies were being allowed to avoid scrutiny because there was no obligation on water companies to follow either Environment Agency or Ofwat guidance to classify all storm overflow discharges. Stuart Singleton-White, the head of campaigns at the Angling Trust, said untreated sewage was being released into rivers routinely, after just light showers. He said: “If Boris Johnson is serious about investing in a post-Covid-19 recovery, one of the first things he can do in order to address a green recovery and to create thousands of jobs is to make tackling the scandal of sewage pollution in our rivers an absolute national priority. “This is a public health issue because so many people are using our rivers. This is a systemic failure and it should not be allowed to happen.” Singleton-White said there was no reason the large infrastructure works required to stop the use of CSOs to release raw sewage could not be carried out. “If you can build the HS2 railway from London to Birmingham, you can address sewage overflows into rivers,” he said. The Environment Agency gives water companies permits to release untreated human waste and rainwater into rivers via CSOs. More than 60 from one CSO should trigger an investigation by the agency, but the Guardian data reveals some CSOs are discharging hundreds of times. A spokesman for Severn Trent water said it had classified its CSOs but had not published the results. Of 2,954 CSOs, he said 2,782 (94%) were classified as “satisfactory”, 105 (4%) were “at risk of becoming unsatisfactory” and 67 CSOs (2%) had been identified as requiring improvements to meet the standard of satisfactory. The company added: ‘“CSOs are central to the design of sewer systems as they also play an important role in protecting properties from flooding, and the discharges they make are permitted and regulated by the Environment Agency so as not to have a detrimental impact on rivers.” South West Water said: “Water companies are not currently required by the Environment Agency to classify CSOs in this way.” A spokesperson said in 2018-20 South West Water completed an extensive programme to install event duration monitors on its 1,192 overflows. As a result, more than 90% of these now provide data on the start and stop times of any storm water discharges. Thirty-seven overflows were being investigated in relation to their frequency of operation and potential environmental impact. Wessex Water said it had categorised its CSOs and the information was shared when requested. An Anglian Water spokesperson said: “All of our CSOs were assessed in 2004 and we invested to improve any deemed to be unsatisfactory between 2005 and 2010. “Since then, in our region, the Environment Agency has identified no substandard or unsatisfactory storm overflows in need of improvement.” • Statements from the water companies can be read in full here.