The report said drugs are easily available in Pentonville prison
The conditions in a north London prison have been described as a "disgrace to an affluent society" in a new report.
The Independent Monitoring Board's (IMB) annual report into Pentonville Prison, Islington, said the overcrowded prison was putting a "burden" on staff.
It said the accommodation was akin to a "shared lavatory" and the prison has not been upgraded since 1842.
Although the report noted improvements in cleanliness, it highlighted that drugs were easily available.
The report said vulnerable prisoners were forced to follow an "impoverished" regime and there were delays in transferring mentally ill inmates for treatment.
Singer Amy Winehouse's husband Blake Fielder-Civil has been incarcerated in the prison since last year.
The report pointed out that overcrowding in the prison was putting "intolerable burdens upon staff at all levels".
It said: "Most shamefully, the pressures created by unsustainable numbers remain an apparently insuperable obstacle to the elimination of the degrading living conditions which are nothing short of a disgrace to an affluent society."
The report added the only modification since 1842 has been "the re-installation of in-cell sanitation, the effect of which has been to require two strangers to eat, sleep and spend a large part of their waking hours in what amounts to a shared lavatory".
"Continued use of such accommodation, with no plans to upgrade it, is simply not consistent with an avowed decency agenda."
Praising improvement in cleanliness in the past year, the report said: "Staff morale is noticeably better. There is some evidence that unsatisfactory staff/prisoner relations are being addressed."
Juliet Lyon, director of the Prison Reform Trust, said those who think prisons are a "holiday camp" should read the report.
She said prisoners spend their days "sleeping and eating in a large lavatory, while staff struggle to cope with massive overcrowding and high numbers of addicts and mentally ill men in desperate need of transfer to treatment".