He identified violence, drugs, suicide, squalor and poor access to education as prominent themes in his annual report.
The report said the watchdog had found “some of the most disturbing prison conditions … ever seen – conditions which have no place in an advanced nation in the 21st century”.
Clarke suggested that the worsening conditions have come as a result of a lack of resources.
He said it is “noticeable” that increasing levels of violence has “only really taken place in the past five years, at the time when large reductions in staff numbers were taking effect”.
Clarke’s third annual report said that of all safety recommendations made in previous inspections of men’s prisons, 49% were not achieved.
“Of course, I realise that in recent years many prisons, short of staff and investment, have struggled to maintain even basic standards of safety and decency,” the report said.
Clarke praised the Prison Service for recruiting more staff and said he hoped this could “restore basic levels of safety and decency.”
Justice minister Rory Stewart said the government had listened to the inspector’s recommendations and was putting investing £16m into cleanliness and decency and £7m into in-cell telephony.
Stewart said that the ministry was also investing £14m into tackling organised crime and installing new technology like scanners to crack down on drugs.
The Performance Tracker, prepared by CIPFA and the Institute for Government, has highlighted a rise in prison violence following the government’s austerity programme.
The third edition of the tracker is due to be published in the autumn.
