A former prisons chief has warned that running jails unsafely is a "crime" in a scathing critique on the state of the service.
Phil Wheatley highlighted reductions in officer numbers in a highly critical assessment of the Government's handling of the estate in England and Wales.
He said: "It is simply not acceptable in a comparatively rich democratic country to run unsafe prisons that do not provide decent conditions.
"This is not simply a moral issue, but a legal one too; to comply with the Health and Safety at Work Act, which creates legal duties to both staff and prisoners.
"In short running prisons unsafely is a crime and one to which the Health and Safety Commission ought to give more attention."
Mr Wheatley, who retired as director general of the National Offender Management Service in 2010, said the then-coalition government inherited a prison service that was performing better than it had ever done.
But eight years on, he said it was "undeniable" that jails in England and Wales are "in crisis".
Writing in the 2018 edition of The Prisons Handbook, Mr Wheatley acknowledged that Justice Secretary David Gauke, is "too new to have had much impact to date".
But he claimed that Mr Gauke and prison minister Rory Stewart "appear intent on blaming the crisis they have inherited on New Psychoactive Substances (NPS) - rather than budget cuts, poor political decisions and frequent changes of political direction".
Mr Wheatley added: "There is no quick fix, the sad truth is that it is relatively easy to make a good prison bad, but much harder to repair the damage."
Much of the prisons estate in England and Wales has been hit by surging numbers of assaults and self-harm incidents.
There have also been a number of large-scale disturbances, while the availability and use of drugs behind bars has rocketed.
The Government's efforts to tackle the crisis will come under fresh scrutiny on Thursday when the latest official safety in custody statistics are published.
At the weekend the Ministry of Justice revealed that it had passed a target to recruit 2,500 additional prison officers seven months ahead of schedule.