Southern Water’s environmental performance slammed by regulators as MP calls one-star rating 'damning'
Southern Water had 301 pollution incidents in the last year
A new report on the performance of the water industry has labelled Southern Water’s environmental performance as “poor”, while Portsmouth Water remains one of the highest rated water companies by customers.
The Water Industry Performance Insights Report, published jointly by the Drinking Water Inspectorate, Environment Agency, Ofwat and Natural Resources Wales gives an overview of individual water companies’ performance.
The report found that while Southern Water’s drinking quality is “exceptional”, the company's environmental performance is “poor”, receiving a one-star environmental performance rating from the Environment Agency
The report said: “Although it has a high level of pollution incident self-reporting, which enables early intervention, the high numbers of incidents, including serious incidents remains a concern.”
In the last year, Southern Water has had 301 pollution incidents, with 12 of those being classed as ‘serious’. 84% of pollution incidents were self-reported by the company, and the provider has 11 treatment sites not compliant with sewage discharge limits.
The report said: “We expect the company to implement preventative measures to reduce their occurrence. It has also failed to complete all necessary environmental improvement actions on time and has poor compliance with discharge permit numeric limits for pollutants in wastewater at treatment work sites.
“We expect the company to improve internal sewer flooding performance. Customers also report the lowest levels of satisfaction in the industry. It must substantially improve customer interactions and overall experience.”
However, the report also noted that: "Consumers can be confident that their water is safe to drink. (Southern Water) has reported its strongest-ever performance for minimising water supply interruptions, providing customers with a more reliable water supply.
“The company has reduced leakage considerably and has maintained household consumption levels below the industry average, helping to protect future water supplies.”
Liz Jarvis, MP for Eastleigh, said: “Yet again, Southern Water has been shown to be failing customers and the environment. The one-star rating from the Environment Agency is damning. Bosses losing out on bonuses as a result is a welcome penalty, but it’s small consolation to customers whose bills have been hiked year after year.
“It’s more urgent than ever for the Government to fix the water industry. Customers should not be paying for years of underinvestment while shareholders rake in profits. Families are paying ever higher bills, and in return Southern Water has been ranked the worst company in the country for customer satisfaction. Bosses should never have been in line for bonuses while this is going on. It is clear that Private water companies have put profit ahead of people for too long.”
Tim Mcmahon, chief operating officer of Southern Water said: “Ofwat’s report says Southern Water’s performance is ‘improving’, recognising the progress we’re making in key areas, though we’re not yet out of the lower category.
“Last year, we reduced water supply interruptions by 96%, cutting the average time customers were without water from more than 2 hours the year before to just over 5 minutes. Ofwat has showcased that improvement, featuring it as a case study. Among other improvements, we got external sewer flooding down by 18%, and we cut leakage by 12%.
"The EPA rating from the Environment Agency is disappointing but was expected, reflecting the challenges we faced in 2025 operating ageing infrastructure during periods of extreme weather and intense rainfall. We have reduced overall pollutions by almost a third since 2023, but we know there’s much more to do.
“Backed by a record £8.9bn investment, we’re tackling the root causes of pollutions -- including increased monitoring and technology to detect and remove blockages, replacing ageing infrastructure, improving maintenance and strengthening power resilience at high-risk sites. These are the actions needed to achieve better outcomes for customers and the environment. Meaningful change won’t happen overnight, but we’ve made significant progress since launching our turnaround plan, and we’re determined to continue that improvement.”
Portsmouth Water, a clean water-only provider, was found to have one of the highest compliance rates in the water industry, with drinking water of an “exceptional standard”, and registered no serious incidents of pollution.
The report said: “The company has also effectively managed risk of discoloured water. It has one of the lowest consumer contact rates, which demonstrates high levels of consumer confidence. Customers report some of the highest levels of satisfaction compared with others in the industry.
“Although reported water supply interruptions performance has deteriorated, the company is still one of the best performers in the industry. The company performs well environmentally with low pollution incident numbers (2 incidents) and no serious incidents. It has high levels of incident self-reporting, supporting swift intervention and helping to minimise environmental harm.”
Portsmouth Water customers have experienced more interruptions in water supply in the past year, with average minutes of lost supply per property more than doubling from the previous year.
The report also noted a “marked increase” in total water leakage, with a 18.7% increase compared to the previous year.
“Although better than the industry average for leakage per property, the company reports a marked increase in total leakage,” the report stated.
“It is also worse than the industry average for household consumption. It needs to reduce leakage and encourage household water efficiency to protect the environment and ensure there is enough water for future demand.”
Philip Duffy, Chief Executive at the Environment Agency, said: “People expect two simple things: safe water from their taps and clean, healthy rivers. Today’s report shows good performance on drinking water quality, but on wastewater and pollution the sector is still falling short.
“We are stepping up inspections and enforcement and will use our powers to hold water companies to account and drive the improvements people and the environment deserve.”
Helen Campbell, Interim Executive Director for Delivery at Ofwat, said: “Customers rightly expect the record investment approved by Ofwat to deliver tangible improvements in their daily lives and for the environment.
“Over the past year we have seen some step up to this challenge, but this is inconsistent and poor performance continues in too many places. The responsibility sits with water companies to deliver on what they have agreed to, and we will continue to work across regulators to drive stronger outcomes.”