Prisoners at Saughton are being kept in their cells for up to 22 hours a day, a new report reveals.
Inmates also complained of only being allowed an hour outside on two days a week, as opposed to the entitled seven days.
The lockdown only affects those “on protection” according to an assessment by HM Chief Inspector of Prisons for Scotland, David Strang.
“The most pressing challenges facing the prison related to the complex nature of the population mix,” said Mr Strang.
“This had an impact on a range of activities and experiences for the prisoners.
“Disappointingly this situation had been highlighted in previous reports.
“In particular prisoners who were held on protection experienced very restricted regimes and spent too many hours locked in their cells.”
Inspectors will now monitor how much weekly access all inmates get to the open air.
There were positive arrangements for released prisoners, though suitable accommodation remained an issue.
“Overall we found HMP Edinburgh to be operating effectively, providing a safe and secure environment for the prisoners and staff,” said Mr Strang.
Managers at Saughton told inspectors all prisoners were offered an hour in the open air seven days a week.
A Scottish Prison Service spokesman said prisoners “on protection” often refuse to mix with others for fear of being attacked.
“It’s a largely positive report,” added the spokesman. “It recognises the hard work of staff being done.”
Mark Day, head of policy and communications at the Prison Reform Trust, said: “Every prisoner should have daily access to the open air.
“Reports that some prisoners are having to spend 22 hours a day locked in their cells are unacceptable, and certainly merit closer scrutiny, as the inspectorate has promised to do.”