London's busiest jail is "overrun with cockroaches" and has an "unusually high" number of assault allegations against staff, a report has said.
The report said prisoners "lacked basic requirements"
The Chief Inspector of Prisons, Anne Owers, published her findings into Pentonville Prison following an unannounced inspection in June.
Ms Owers also accused the jail of "institutional disrespect" of inmates.
The Prison Service said Pentonville's governor was taking a robust stance in dealing with prisoner complaints.
The chief inspector's report revealed 43% of prisoners, down from 64% in 2005, said staff treated them with respect.
Allegations of victimisation rose from 29% to 40% over the same period.
Of 12 main recommendations made in a report last year, seven had not been achieved and another four had only partially been met.
This year's inspection also found 55% of prisoners said they felt unsafe and 42% claimed it was easy to obtain drugs.
Ms Owers' report also said inmates at the north London prison lacked basic requirements such as pillows, while at times there was not enough food.
She said her findings highlighted the scale of problems in "overcrowded and pressurised" local prisons.
"They [managers and staff] need to explore the reasons for the significant deterioration in staff-prisoner relationships, monitor them closely and take decisive action to investigate and deal with any allegations against staff," she said.
"They found some improvements: prisoners were out of their cells more than they had been," Ms Owers told BBC Radio 4's Today programme.
"But we did find a deterioration in relationships with staff. I think what we did find was that the new management team had inherited a prison with virtually no systems for making sure that prisoners got the basics they needed, and for managing and monitoring the behaviour of some staff.
"What they were faced with is the rising prison population, the fact that they've no headroom, the fact they've got a hundred prisoners sometimes coming in a day.
"It's a very difficult environment in an old building in which to try to make the kind of changes Pentonville needs," Ms Owers said.
The prison was said to be "overrun with cockroaches and vermin" caused by leftover meals and flour sacks left open in the kitchen.
But a Prison Service spokeswoman said: "Pentonville now has a pest control programme in place which includes a pest control company visiting the site on a weekly basis."
She added that although food occasionally runs out due to poor portion control, no prisoner goes without a meal.
Michael Spurr, from the Prison Service, said: "We have strengthened the senior management team and the governor is taking a robust stance in dealing with allegations of inappropriate behaviour by staff.
"Pentonville has been operating under significant pressure. As the chief inspector acknowledges, it is the busiest prison in London."
Shadow home affairs minister Edward Garnier made a plea for proper leadership at a "strategic, political level" of the Prison Service.
And Juliet Lyon, of the Prison Reform Trust, called for the Home Secretary to consider closing Pentonville as it was "not fit for purpose".
She added: "The Pentonville of this report would be more in place in Hogarth's Gin Lane than Islington today."