The “explosion” of violence that has hit jails will continue while inmates are held in “utterly appalling” conditions, the prisons watchdog has warned.
Peter Clarke said prisoners are “frustrated and angry” at being locked up for as long as 22 hours a day.
Mr Clarke said: “The Government’s ambition for prison reform will not be achieved unless prisons are made safer, the problem of drugs is dealt with and living conditions are improved.”
There have been rises in the number of assaults, self-harm incidents and suicides in prisons in England and Wales. A number have been hit by serious disturbances. In the latest episode trouble flared at Long Lartin maximum security jail on Wednesday.
Earlier this week a report on living conditions across the estate warned that inmates are turning to drugs to “break the boredom” as they are locked up in cramped and decrepit cells for up to 22 hours a day.
The assessment detailed how some cells have broken windows, poor ventilation and heating, graffiti, damp, exposed wiring or vermin infestations.
Mr Clarke, the chief inspector of prisons, told BBC Radio 4’s Today programme: “The inevitable outcome of the conditions in jail and the crowding is that prisoners are very frustrated and angry.
“We have seen an explosion of violence in our jails over the last few years.
“Until things are improved in terms of the frustrations of prisoners in their conditions and being locked up for excessively long periods of time during the day, I’m afraid I can’t see how things are going to improve.”
Referring to the findings of his report on living conditions, Mr Clarke said: “I hope it showed graphically the utterly appalling and unacceptable conditions that do prevail in far too many of our jails.
“Broken plumbing, blocked lavatories, broken windows, broken furniture, filth, infestations, cockroaches, rats – all the sorts of things that really, in the 21st century, we should be saying ‘this simply is not right’.”
Mr Clarke acknowledged that “in order to go to jail you have to be convicted by a court and sentenced”, but he said: “The punishment should be the sentence, it shouldn’t be the conditions in which you are held.”
He added: “Surely there’s a public interest in making sure that prisoners are held in conditions that give them the opportunity to train, to be educated, to rehabilitate and eventually to be able to return to the community and lead a good and useful life and make a contribution to that community.”
Figures published on Friday show the prison population at 85,463, less than 1,000 below the “useable operational capacity” of 86,456.
Earlier this week the president of the Prison Governors Association said jails are “full to bursting” and called on the Government to “be brave” and cut the numbers behind bars.