Tap water in thousands of homes could have been contaminated with E.coli, a water company has warned.

Sutton and East Surrey (SES) Water has advised people living in parts of Kent and Surrey to boil their water as a “precautionary measure” after a routine test detected a possible outbreak of the bacteria.

The company said water supplies “could be affected” by the bacteria, which can cause severe stomach pain, bloody diarrhoea and kidney failure in humans and animals.

Some 443 affected postcodes include homes in Oxted, Redhill, Horley, Biggin Hill and Tonbridge.

SES Water said in a statement: “Our customers in and around Oxted are being advised to boil their tap water after tests showed that water supplies could be affected by the bacteria E.coli.

“The issue was discovered during routine tests, and our teams are working to investigate the problem and restore supplies to their usual high standards.

“We are working very hard to rectify the situation and are very sorry for the inconvenience being caused.”

SES Water said it is carrying out further tests to confirm the scale of any contamination, and while awaiting the results has advised customers to boil water and let it cool before using it for drinking, preparing food, cleaning their teeth or giving to pets.

The company added that once cooled, boiled water can be kept in the fridge, covered and used within 24 hours.

Most cases of E.coli infections are mild and do not cause a serious health risk, and can be resolved by drinking lots of fluids.

However, some strains can cause severe symptoms and life-threatening complications including hemolytic uremic syndrome, which can lead to kidney failure.