Thames Water has revealed an 18% rise in pollution incidents during the first half of its financial year.
The country’s largest household supplier reported 257 category one – the most serious – to category 3 pollutions over the six months to the end of September.
It said that action to prevent these incidents was a core part of a three-year action plan to improve customer service that had been approved by its board.
Thames, which is looking to raise bills to help pay for much-needed investment in its ageing infrastructure, said: “Our turnaround plan addresses and mitigates the major drivers of pollutions across our wastewater network and sewage treatment works, including more proactive network cleaning and monitoring, and better prioritised reactive responses.
“Consequently, blockages, which cause over 40% of network pollutions, reduced by 5% in the first half of the year.
“As we look ahead, changes our regulators are making to the definition of pollutions are expected to increase the overall number of pollutions we report, even if there is no change in the impact we have on the environment.
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“Notwithstanding this, we are committed to tackle the root causes of pollutions to meet the expectations of our communities and the needs of the environment.”
UK water firms have faced a backlash following a spate of sewage discharges.
In the case of Thames, it was fined more than £3m in the summer over an incident that saw human waste flow into rivers for more than six hours un-noticed.
Performance at Thames has been under particular scrutiny.
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In June, Sky News revealed how fears that Thames could be swept away under the weight of its £14bn debt pile had prompted the government to ready a rescue plan.
Its investors later agreed a further £750m of investment.
Earlier this autumn, regulator Ofwat fined the company £51m for failure to reach its performance targets.
That money will be paid back through reductions to customer bills.
Thames is pushing for the watchdog to allow an increase in bills from 2025 to help fund its investment plans, with the focus on six key areas including tackling leaks, customer complaints, supply interruptions and pollution.
Interim co-chief executives Cathryn Ross and Alastair Cochran warned the turnaround would take time.
“Whilst business resilience remains fragile with frequent failures in our ageing infrastructure, we have taken a risk-based approach to improve reliability by more closely managing core assets and we have started to bring greater rigour to maintenance practices.
“We have also developed long-term asset plans to build resilience and redundancy that will ultimately restore operations to a level our customers expect.”
Thames revealed an 11% rise in revenues to £1.2bn over the six month period.
While underlying profits rose 22% to £627m, its bottom line profit before tax came in more than 50% lower at £246.4m.