Drugs are rampant and inmates live in degrading and overcrowded conditions with nothing to do at Pentonville, a damning report said today.

Random tests showed 15 per cent of prisoners have illegal substances in their bloodstream at any time - while a drugs black market is behind gang problems and violence, according to the latest report of Pentonville’s Independent Monitoring Board (IMB).

The board painted a bleak picture of life in the prison, in Caledonian Road, Holloway, and said cuts could make matters even worse.

David Miller, chairman of the Pentonville IMB, said: “HMP Pentonville is an overcrowded and physically decaying prison, where most inmates share a bleak cell designed in 1842 by the Victorians for one occupant. They live and eat with another prisoner in a cramped space with an open lavatory.

“We are seriously concerned about the prospect of reconciling additional budgetary cuts with the prison’s prime objective of reducing reoffending after release.”

The report revealed inmates get little education or training, with half the roughly 1,230 prisoners doing nothing all day, and said the “poor physical environment” desperately needs upgrading.

Mr Miller added: “As well as being a punishment, prison should also be an opportunity for the inmates – many of whom have slipped through the net in terms of education and training – to acquire life skills to increase their chance of finding honest employment.”

The IMB did welcome improvements over the year from April 2010 to March 2011, and commended the efforts of staff – saying the failures were down to stretched resources and outside the prison’s control. It added work has been done to crack down on drug smuggling and corruption.

A Prisons Service spokeswoman said: “We take the illicit use of drugs in prisons and the problems they cause incredibly seriously. We are working hard to keep contraband out of prison, using a range of security measures to reduce drug supply, including working closely with police forces and carrying out random mandatory drug tests.”