The prisons watchdog has demanded the Government intervene to save lives and protect prisoners at a "fundamentally unsafe" jail.
Peter Clarke used a new "urgent notification" system for the first time to put Justice Secretary David Gauke on notice that immediate action is needed at HMP Nottingham.
Mr Clarke, chief inspector of prisons, said: "It appears that the problems at Nottingham are intractable and that staff there are unable to improve safety despite the fact that this failing increases the vulnerability both of those who are held in the prison and of those who work there."
Under the new urgent notification process introduced in November, the Chief Inspector can inform the Secretary of State of any urgent and severe prison problems found during an inspection.
The Justice Secretary then has 28 days to publicly report on measures adopted to resolve the issues.