Prisoners are merely being "warehoused" at a jail where they are kept in squalid conditions for up to 23 hours a day, a watchdog report has warned.
Under a restricted regime, inmates at HMP Winchester are often let out of their cells for only three quarters of an hour a day.
This is insufficient time for basic tasks such as showering, exercising and making phone calls, according to the prison's Independent Monitoring Board.
It said staff shortages have limited searches, leading to an increase in drugs and contraband, with "urgent concerns" about the prevalence of illicit substances including Spice.
Overdoses result in serious illness for the prisoners and cause nausea and excessive fatigue when passively ingested by staff, the Board's annual report said.
While mobile phones, sim cards and improvised weapons are regularly found by staff, monitors reported that quantities of such items remain undetected, resulting in debt problems and violence.
The Hampshire jail became smoke-free last year, leading to some tobacco smuggling and attempts to smoke substances such as tea leaves, the assessment added.
The standard of accommodation at the Victorian facility was said to be "unacceptable", with showers and phones frequently out of order and rubbish thrown from cell windows accumulating outside.
Such conditions provide little scope for rehabilitation and provoke a culture of hopelessness and frustration, leading to bad behaviour, drug abuse, violence, self-harm and an unsafe atmosphere, the IMB said.
Its report, which covers the year to May, noted that the prison was placed in "special measures" in January, but staff shortages, a lack of resources and the diverse population have prevented significant improvement.
The board's chairman Angus Somerville said the jail is "little more than an establishment which fulfils the function of 'warehousing' prisoners, but we feel that much of what is wrong with the prison comes down to a lack of funding and resources".
He added: "This means that the good work we do see happening in Winchester is patchy."
Built in 1846, Winchester operates as a prison and young offender institution, holding male inmates aged 18 and over.
At the end of last month, it had a population of 584.
It is the latest jail to fall under the spotlight after a flurry of highly critical reports sparked fresh scrutiny of the safety crisis that has hit much of the prisons estate in England and Wales.
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