Prisoners are getting high on Spice-soaked stamps which are mailed to them from the outside.
Letters, drawings and photos are often impregnated with the drug and then ripped up and smoked by inmates wanting to get high.
But it has now been discovered that stamps are also being soaked in the class B drug.
A recent report into the 920-capacity HMP Lowdham Grange said officers now use a Rapiscanner, a drug detection machine, to test all mail coming into the jail.
Any mail found to contain traces of drugs is destroyed, although it can be photocopied and passed on to prisoners at the jail where 60% of inmates are serving sentences of 10 years or more, and a third serving whole-life terms.
At least 49% of prisoners also said it was ‘easy’ to get drugs at the Serco-run jail.
The report added that between January and June 2018, 5.5% of prisoners who were randomly tested for drugs tested positive, and this figure rose to 14.2% when new psychoactive substances were included.
Glyn Travis, assistant general secretary of the Prison Officers’ Association, speaking last year, said Spice was a ‘cocktail of chemicals that kill’.
He said: ‘Prisons are awash with drugs and spice is now the cannabis of the 21st century.
‘Spice has become a deadly drug, which causes violence, self harm and suicides – and our staff see it first hand.
‘It a cocktail of chemicals that kills.’
HMP Lowdham Grange, in Nottinghamshire, made the national headlines earlier this week after it was revealed prisoners could now have photos taken with their family at a photo booth installed at the jail.
Bosses at Serco said earlier this week that although the report raised many good points about the jail, it would do more to ‘address the recommendations in the report’.