Help the Santorini Donkeys urged for the rule to be put in place after a surge in the number of “obese” holidaymakers was reportedly leaving the mules with spinal injuries.

Donkeys have traditionally been used to transport people over hilly areas of the Greek island which vehicles cannot access.

Animal rights activists claim a rise in overweight visitors is forcing donkeys to carry ever-heavier loads while they already work long hours with little shelter, rest and water.

A spokesperson told MailOnline: “It’s recommended that animals should carry no more than 20% of their own body weight.

“The obese and overweight tourists, combined with the lack of shade and water as well as the sheer heat and 568 cobbled steps, is what is causing such a problem.

“There should be a weight restriction. With donkeys, it should be no more than eight stone, but how would that be imposed and who would be there to make sure that happened?

“Now they’re having to resort to using cross-bred mules, because the donkeys just aren’t strong enough.”