Hindley prison deemed one of the worst jails in scathing report
The regime at a prison near Wigan was one of the worst of its type to be seen by a watchdog, according to a damning inspection report.
HMP Hindley housed inmates that were regularly locked in their cells for more than 24 hours, leaving them unable to attend work or education.
HM Inspectorate of Prisons also found levels of violence at the Category C facility to be "very high" for a prison of its type.
A survey of prisoners indicated it was "far easier" to get hold of drugs than clean clothes, bed sheets or books.
The report is likely to intensify controversy over the condition of prisons in England and Wales, after campaign group the Howard League for Penal Reform warned on Monday that suicides in prisons in England and Wales have reached "epidemic proportions".
HMP Hindley's residential wings and landings were dirty, with inspectors finding mould and fungus.
Prisoners also struggled to access basic entitlements such as showers.
Peter Clarke, Chief Inspector of Prisons, said: "The regime at Hindley was one of the worst, and possibly the very worst, that inspectors had ever seen in this type of prison.
"The length of time for which young adults and adults alike were locked up was, in our considered view, unnecessary, unjustifiable and counterproductive."
Mr Clarke added: "Almost every aspect of prison life for the prisoners was adversely affected by the regime."
The prison held 515 males at the time of the inspection in July.
Peter Dawson, Director of the Prison Reform Trust, said: "We are used to dreadful inspection reports about dilapidated, overcrowded Victorian prisons. HMP Hindley is none of these things, and this damning verdict is all the more troubling as a result."
Earlier this month, thousands of officers stopped working to protest high levels of violence and self-harm in prisons.
The government has unveiled plans to reform prisons with measures such as employing an additional 2,500 officers, and preventing the use of drones to drop drugs into jails.