Anglian Water “has not shown significant improvement over the past five years” and was responsible for 10 serious pollution incidents last year, a government watchdog has concluded.

Together with Thames Water, it was responsible for more than half of all serious pollution incidents involving England’s regional network of nine privately-owned water and sewerage companies in 2020, according to the Environment Agency (EA).

But the company has improved on its performance in 2019 — when it was awarded two stars (requiring improvement) out of a maximum of four — to three stars (good) in 2020.

Last week, Southern Water was fined a record £90m for causing 6,971 unpermitted sewage discharges. Along with South West Water, Southern remains at the bottom of the EA’s latest Environmental Performance Assessment’s (EPA) table with two stars.

Thames Water was also awarded three stars, but five companies — Northumbrian Water, Severn Trent Water, United Utilities, Wessex Water and Yorkshire Water — achieved 4 stars — although certain improvements are still required.

Anglian Water serves nearly 7m customers in the East of England and Hartlepool.

EA chairwoman Emma Howard Boyd said it was welcome news more than half the sector had achieved the highest rating but added: “The performance of some companies gives us serious cause for concern. Southern Water and South West Water remain at the bottom of the table. South West Water has received a two star rating for the entire five years of the EPA and this drags down the whole sector’s reputation.

“Anglian and Thames Water have not shown significant improvement over the past five years, and more than half of all serious incidents in 2020 were from the assets of these two companies.”

Overall, Anglian Water was found to be responsible for 210 pollution incidents in total in 2020, compared to 266 in 2019. It was given an amber rating (slightly worse than target) for this, and for the 10 serious pollution incidents — down from 2019 when 12 serious pollution incidents were recorded placing it in the red (significantly worse than target) category.

The company was also rated amber for self-reporting pollution incidents. It reported 73% of incidents in 2020 — or 170 in total, while 62 incidents were reported by others.

An Anglian Water spokeswoman said the company was “pleased” to have regained its three star status.

“The number of pollutions we deal with has fallen this year, and while we’ve met our targets over the last five years we know there is much more to do as we move towards a goal of having none at all,” she said.

“2020 has seen us achieve some of the best water recycling works compliance we have ever seen as well as deliver an unprecedented number of investment schemes as part of the Water Industry National Environment Programme (WINEP) including the cessation of our abstraction in the environmentally sensitive Ant Valley, which includes Catfield Fen SSSI.

“Our region is vulnerable from the effects of a changing climate and the risk of flooding and is also one of the fastest growing.

"The only way we can tackle these challenges is through continued investment in technology, improving our ability to monitor, predict and respond to incidents and to ensure our treatment processes are able to meet ever tightening environmental standards.

"We are also committed to ensuring we have the resilience in our ground and surface waters to ensure we can meet increased supply demands without causing environmental harm and to achieving our ambition to protect and enhance the unique chalk stream habitats across our region.”