Summing up the situation in a letter to Mr Stewart in May, the board said the institution “fails to provide a safe and decent environment on an almost daily basis”.
The letter, which Mr Stewart responded to, listed deaths in custody, drugs being widely available and violence among its concerns.
Specific examples of problems included a prisoner who returned to a blood-spattered cell after his fellow inmate had been assaulted. He was given replacement bedding that was soiled, the board said.
Cell toilets with no screen, broken showers and “ever present” cockroaches contributed to the “unfit” living conditions, it added.
The letter, from IMB chair Roger Swindells, said: “I am writing to you to express our very serious concerns regarding this establishment, where basic humanity, safety and purposeful activity is simply not being delivered.”
The board said that while many workers had tried to support prisoners, it had to conclude that the jail was “unsafe for prisoners and staff”.
Mr Swindells said they had planned to release the letter next month to coincide with the annual report but have published it early given the report by the chief inspector of prisons and decision of the Government to take control.
Mark Leech, Editor of The Prisons Handbook asked why the IMB ‘had not gone public’ about conditions.
Mr Leech said: “The IMB system of monitoring is in complete disarray, its no good writing letters to the Minister when what is needed is for the public to be made publicly aware by the IMB of how dangerous the prison is for both prisoners and staff – their loved ones who live and work inside the jail deserved that courtesy.
“Instead the timid IMB resort to writing a letter, and now three months later it took an inspection from the Prisons Inspectorate to call a halt to the decrepit and dangerous conditions inside the jail.
“I have said it before and I will say it again: we are always let down by the dysfunctional IMB watchdog that is scared of standing up and speaking out – that is not the kind of independent robust courageous statutory watchdog that Parliament envisaged when it created the IMB and we all deserve better from it.”