SPICE will only be eradicated from Scotland’s jails when they are properly staffed, the Prison Officers Association (POA) said yesterday, after an expert called for inmates to be given cannabis to combat the menace.

Pharmacologist Stephanie Sharp, a co-founder of Glasgow’s Expert Witness Service, said cannabis was a “much safer” substance than spice.

Herbs soaked in synthetic cannabinoids — marketed as spice or K2 — became a popular “legal high” alternative to weed in the 2000s and have since been made illegal.