Food costs at HMP Edinburgh have been cut drastically following a clampdown on prisoners claiming to be Jewish.
In 2017, inspectors called for an investigation into why more than 100 inmates were receiving kosher meals - which are more expensive to produce than standard prison food - even though only nine prisoners across the country were classes as Jewish the year before.
It emerged prisoners were understood to be converting to the faith in a bid to receive the meals.
Today, The Times revealed fewer prisoners are now requesting kosher meals, resulting in less money being spent on food.
A prison source is quoted as saying: "The number of Jewish prisoners is negligible - I think we had two in 2014. Ever since one guy converted to Judaism we've seen a huge rise in the number claiming to be Jewish as they saw the meals were better."
Tom Fox, of the Scottish Prison Service, added: "We had a number of people who claimed to be Jewish and [in need of] need kosher meals and in all probability weren't.
"There were new guidelines put out with regards to people applying for a kosher diet and that has tightened the system up and reduced the number. Basically, the system before was that people said they were Jewish so required a kosher diet, and in some places they received it.
"If someone requires a kosher diet they will get it but when we tightened up the requirements and made it slightly more bureaucratic, people suddenly decided they weren't."
The number of prisoners claiming kosher meals in Edinburgh has dropped by more than three quarters to 23.
Regular prison meals cost about £2 per day per prisoner in 2017 while kosher food was more than £8. The total extra cost was almost £250,000 a year.