NHS hospitals are asking zoos and vets to scan patients who are too large to fit into hospital scanners.

As the UK population grows increasingly obese, CT scanners, normally intended for four-legged animals at the UK’s leading veterinary college in north London, are being requested for human use.

The Royal Veterinary College (RVC) said its CT scanners, customised for horses, could be used to accommodate patients weighing 30 stone or more, but it would first have to acquire a special licence to scan humans.

In America,where obesity has reached epidemic levels, patients are routinely referred to zoos.

A spokesperson from the Imperial College Healthcare NHS Trust, which oversees St Mary's Hospital, said: “We have never referred or been asked to refer a patient to London Zoo or the Royal Veterinary College for scanning.”

London Zoo also denied taking obese patients, but a spokeswoman for the RVC confirmed that it has been approached.

It is not known whether any veterinary colleges are seeking licences to perform the procedure.

The CT scanner at the RVC, housed in the equine hospital, is used with a specially built table to support anaesthetised horses.

Millions have been spent on callouts by Britain’s fire crews who are having to shift obese patients stuck in the bath or their bedrooms and who cannot be safely lifted by ambulance staff.

A report last year warned that the NHS is ‘poorly prepared’ to deal with obese patients