The sugar-rich Western diet is fueling a superbug which has evolved to thrive in hospitals, scientists have warned.

The gut-infecting bacterium Clostridium difficile (C.diff) is evolving into two separate species, with one group increasingly adapting to live in the guts of people with poor diets, while growing ever better at avoiding the harsh disinfectants used to clean wards.

More than 13,000 NHS patients each year are infected with C.diff, which can cause debilitating diarrhoea and leave sick people dangerously dehydrated.

Bacteria are also becoming increasingly resistant to antibiotics, and if not treated quickly enough an infection can be fatal. Nearly 2,000 people die from the bacterium each year in Britain.

Researchers at the Wellcome Sanger Institute and London School of Hygiene & Tropical Medicine looked at the genetic differences of 906 strains of C-diff taken from humans and animals and the environment across 33 countries.

They found that a dangerous new species is rapidly emerging which can evade common hospital disinfectants and spread easily. And poor diets are making the problem worse.

Dr Trevor Lawley, the senior author from the Wellcome Sanger Institute, said: “Our study provides genome and laboratory based evidence that human lifestyles can drive bacteria to form new species so they can spread more effectively.