“Government neglect” has “directly contributed” to the rise in violence and drugs at HMP Pentonville, the prison’s watchdog said.
The Pentonville Independent Monitoring Board (IMB) called for funds for improvements “as a matter of urgency”.
Justice Secretary Robert Buckland and Prisons Minister Lucy Frazer were asked to visit the Islington prison.
The Ministry of Justice (MoJ) said it had “no illusions” about the challenges facing the jail.
Violence at the prison has increased by more than 50% since 2017, the chief inspector of prisons Peter Clarke found.
Crimes at the prison were driven by gang affiliations, drugs, debt, according to Mr Clarke’s report.
In March, four officers and about 40 prisoners were attacked each week, the IMB said.
Illegal substances were “pervasive”, according to the IMB, which is made up of members of the public to monitor the day-to-day life in the prison.
Less than half of the private workforce “required to maintain the building to health and safety standards, were in place”, the IMB said.
“The board believes this neglect directly contributed to the violence, drugs and self-harm.”
Opened in 1842, Pentonville is one of the country’s busiest prisons, with about 33,000 movements a year through its reception.
At the end of last month, the state-run jail was holding 1,082 men. However, the IMB said the jail was only “certified to hold 900”.
‘Money desperately needed’
The IMB also raised concerns about the prevalence of insecticide-resistant cockroaches and mouldy, broken showers.
It said HMP Pentonville “desperately needs money now to raise the standard of day-to-day life for prisoners and staff and deliver its dual function of serving local courts and helping prisoners lead productive lives”.
An MoJ spokesman said the new management team had made significant improvements since the inspection.
“Those changes include a new drugs strategy combining more cell searches with better addiction treatment, providing more money to refurbish cells, and appointing specialist staff members to work on reducing violence,” he said.
He added government had given an extra £100m for airport-style scanners and mobile phone blocking technology “to boost security and cut violence in our prisons”.