A change in manufacturing process at a Chinese factory is thought to have led to some packs of valtarsan being contaminated with a carcinogenic substance

A blood pressure drug taken by tens of thousands of people in Britain is being withdrawn over fears that some supplies are contaminated with a chemical that causes cancer.

Patients with conditions such as high blood pressure and heart failure have been urged to check their medication as regulators recall packs of valsartan made by two companies.

A Europe-wide alert has gone out after a change in manufacturing process at a Chinese factory was found to result in medicine containing a carcinogenic substance.

The recall applies to valsartan made by Dexcel Pharma and Accord Healthcare, formerly known as Actavis Group. The Medicines and Healthcare Products Regulatory Agency (MHRA) said that patients should be switched to supplies made by other companies.

Sam Atkinson, of the MHRA,