Inmates at Scotland’s small open estate jail are caught with mobile phones an average of once every two weeks more often than those at sprawling Barlinnie.
Freedom of information figures for the last five years showed 123 prisoners had been found with devices at Castle Huntly, between Dundee and Perth, since 2011, despite the jail housing just 230 convicts at any one time.
In comparison, wardens at neighbouring Perth Prison, population around 620, confiscated just 96 phones and officers at Scotland’s largest jail, Barlinnie, removed 122.
Across the country there were 437 inquiries into Facebook use from prisoners while behind bars and a total of 1,813 phones detected an average of more than one every day.
Every prison in Scotland investigated inmates accessing the social media site within the last five years.
There were 22 such probes at Castle Huntly and 30 at Perth.
An SPS spokeswoman said: “We do not permit access to the internet and therefore to social media sites.
“The SPS only has the ability to investigate and request removal of Facebook accounts that are proven to be accessed while a prisoner is in our care.
“The possession of a mobile phone in prison is a criminal offence.
“If we receive information to suggest that prisoners are in possession of such devices we will take all appropriate action and report it to the relevant authorities.”
This summer the SPS admitted officers deleted the accounts of 55 Facebook users in 2014 and 2015 alone.
Last month The Courier revealed complaints about the “physical environment” were among a catalogue submitted by prisoners at Castle Huntly.
The inmates who are allowed regular unsupervised trips out in public also saw fit to complain about their home leave on almost 20 occasions within the last year, compared with just one prisoner at Perth.