The safety of inmates at Britain's biggest prison is in jeopardy, bullying is not properly tackled and relations with staff are strained and even abusive, inspectors have warned.
In a damning report, Nick Hardwick, the Chief Inspector of Prisons, said the treatment of many offenders at Wandsworth jail was "demeaning, unsafe and fell below what could be classed as decent".
He protested that managers seemed unwilling to tackle problems at the 1,650-inmate prison in south-west London. Mr Hardwick said progress in improving the regime at the 160-year-old prison, which holds "a challenging population with multiple problems", had stalled with high levels of self-harm and inadequate protection for the victims of bullying.
He warned that prisoners' safety was now "a matter of serious concern" and called on the Prison Service management to "act decisively" to reverse the jail's decline.
The inspectors said: "Wandsworth compared badly with similar prisons facing similar challenges and we were concerned by what appeared to be unwillingness among some prison managers and staff to acknowledge and take responsibility for the problems the prison faced."
Levels of self-harm and self-inflicted deaths were high and inspectors "observed indifference and disinterest from staff and, on a few occasions, abusive language towards prisoners". The report also found that some prisoners were out of their cells for just two hours a day.
Others who were stabilising from drugs or detoxing from alcohol were transferred out of a unit where they could be closely monitored before stabilisation was complete, a situation described as "potentially dangerous" by the inspectors.
There also appeared to be little attempt to resolve underlying reasons for the behaviour of prisoners who were transferred to the segregation unit, they said.
Frances Crook, chief executive of the Howard League for Penal Reform, said: "Prisoners are being detained in revolting conditions. Such abuse hampers safe return to the community and puts victims at risk."
Geoff Dobson, deputy director of the Prison Reform Trust, said: "This shocking report, one of the worst I can remember, shows how quickly and how far a large prison can go downhill. The chief inspector has exposed an establishment that was in some respects close to a warehouse, leaving many of those in its charge more damaged than when they were taken in through its gates."
Michael Spurr, chief executive of the National Offender Management Service, admitted it was a poor report, but said action had already been taken to tackle problems. "I visited the prison last week and I am satisfied improvements are being made," he added.