The latest damning report into conditions at HMP Pentonville has again cast doubt on the Victorian prison’s future.

An unannounced inspection at the jail, the results of which were published this week, said the prison was seriously overcrowded with 1,236 men – 35 per cent more than capacity.

It found around 200 of the inmates recovering from heroin addiction, with positive drug testing rates high and 30 per cent claiming it was easy to get drugs.

Meanwhile almost half of the convicts said they felt unsafe, an average of 19 self-harmed each month and 60 were one suicide watch at any one time.

Despite this, the document praised Pentonville for making improvements and congratulates staff and governors for working “heroically against the odds”.

The report, penned by Nick Hardwick, her majesty’s Chief Inspector of Prisons, said: “It is clear that Pentonville cannot operate as a modern 21st century prison without investment in its physical condition, adequate staffing levels to manage its complex population and effective support from the centre.

“If these things cannot be provided, considerations should be given to whether HMP Pentonville has a viable future.”

Independent cllr Greg Foxsmith, a criminal defence lawyer, said: “Everyone who lives or works in Islington should be shamed by the barbaric, over-crowded vermin-infested institution of Pentonville prison.

“Those politicians who pander to the tabloid myth of prison as a ‘holiday-camp’ should read and reflect on this report.”

In 2011, a report by the prison’s Independent Monitoring Board (IMB) found drugs were rampant and inmates live in degrading and overcrowded conditions, while last year a think tank proposed closing the jail and merging it into a ‘super prison’ – an idea backed by ward councillor Rupert Perry.

Michael Spurr, chief executive officer of the National Offender Management Service (NOMS), said: “I am pleased that the Chief Inspector recognises that progress has been made at Pentonville in important areas despite the challenges inherent in running a large, old prison with a highly transient and challenging population.

“The reduction in violence and the advances in resettlement are particularly noteworthy and the former governor and staff deserve credit for the progress made.”