Most cases of C. difficile are not actually caused by the bug being spread round hospitals, a study suggests.

A team from the University of Oxford said “more and more deep cleaning ain’t going to do any good”.

Analysis of every C. diff infection in Oxfordshire for more than three years showed less than a fifth of cases had been spread between hospital patients.

Researchers said there was a growing awareness of animal and community sources of infection.

The gut bug is one of the most feared “hospital infections”. It can be difficult to treat and deadly, especially in the elderly.

Rising levels of a particularly dangerous strain of the bacterium, alongside problems with the MRSA superbug, led to a deep-clean campaign across hospitals in the UK, and infection rates fell.

However, a study in the Oxford University Hospital NHS Trust area, between 2008 and 2011, showed that reducing cases even further may require a different approach.