UNITED Utilities has been told to clean up its act by the Environment Agency which said it must improve its performance.

The agency described as "simply unacceptable" the efforts of water companies to protect the environment after the report, published today, revealed only one of England's major water and sewage companies was performing at the level expected.

The report comes after United Utilities paid out more than half-a-million pounds after chemical leak killed a "significant" number of fish in the River Douglas at Horwich.

United Utilities was given three stars, meaning it must improve its performance to reduce its negative impact on the environment. It was a drop from its previous industry leading four-stars.

But the agency did praise some areas of the firm's work ­— including United Utilities reporting the best performance across the industry on serious pollution incidents.

An Environment Agency spokesman said: "Pollution incident performance continues to be industry leading. UU’s liaison with us on environmental issues is good and the past year has seen close working on the development of PR19 plans; development of their integrated catchment work and improved engagement on flood risk.

"Permit compliance performance, particularly at wastewater treatment works, still needs improvement. UU are improving water resources resilience by embedding the learning from the prolonged dry weather in 2018 and continuing to build their industry leading work on developing integrated catchment solutions, in line with the 25-year plan."

Steve Fraser, chief operating officer at United Utilities, said: “The Environment Agency has given us a three-star 'good' rating for our environmental performance as we exceeded four of the six performance measures. However we are disappointed to have narrowly missed the four-star 'industry leading' rating we have achieved since 2015. The report does not reflect our hard work and financial commitment to protecting the environment here in the North West.

“Last year we delivered 53 environmental improvement projects but we were penalised because two of these schemes were completed 12 weeks late. The report does not take account of four additional improvement projects we delivered ahead of schedule.”

Dr Toby Willison from the Environment Agency said: “Water companies need to clean up their act. People expect water companies to improve the environment, not pollute rivers and ensure secure supplies of water.

“With only one exception, none of the companies are performing at the level we wish to see, the country expects and the environment needs. We will continue to challenge CEOs to improve company performance and we will take strong and appropriate enforcement action.

“Companies performing well have a positive ripple effect on the natural environment and communities in their regions. We want all water companies to meet the expectation of their customers, the needs of environment and learn from the best practice that the leading company is demonstrating.”

Northumbrian Water was the only company achieving the highest four-star rating, showing that it is possible to bring in good environmental practices and limit the impact of operations on nature.

The Environment Agency report said this improvement is to be applauded which had only been possible with focus from the top of the organisation and ongoing effort from operational teams.

Also dropping to three stars from four were Severn Trent Water and Wessex Water, while Anglian Water and Thames Water remained on three stars.

Southern Water, South West Water and Yorkshire Water were each given two stars and described as demonstrating an "unacceptable level of performance".

Most water companies look set to fail to meet 2020 pollution targets.

n Last year United Utilities was fined £200,000 for failing to deliver safe drinking water in 2015 on two occasions.