London gang rivalries are fuelling violence at a “fundamentally unsafe” jail in the Midlands, staff suspect.

An inspection report noted that HMP Onley, near Rugby in Warwickshire, has taken a rising number of inmates from the capital in recent years.

At the time it was assessed in November, around 80% of the population was from the London area.

HM Inspectorate of Prisons found violence was higher than at similar category C prisons.

Although prisoner-on-prisoner assaults and fights had decreased, assaults on staff had more than doubled from 25 to 53 in the previous six months.

Security personnel pointed to violence, drug use and gang affiliations as the main threats to stability at the jail.

The report said: “Around 80% of the population came from the London area, and prison staff continued to suspect that many incidents had been due to gang-related conflict which had arisen in their communities or in previous prisons.”

Very little was done to understand, analyse and map prisoners’ affiliations and potential conflicts, the inspectorate added.

Its report also said:

– A substantial number of prisoners were “self-isolating” or restricted to the wings

– Drugs were too readily available, with 205 emergency health callouts to inmates under the influence of new psychoactive substances – formerly known as legal highs – in three months

– Inspectors saw many examples of poor prisoner behaviour going unchallenged, such as vaping in communal areas and use of foul language

– There were problems with rats and recent attempts to control the infestation had left some dying in wall cavities and vents, leaving an “intolerable” smell in some cells

HMP Onley was given a “poor” assessment for safety, the lowest rating, when it was last inspected in 2016.

Chief Inspector of Prisons Peter Clarke said: “It was particularly disappointing, therefore, to find that at this latest inspection, two and a half years later, the prison was still fundamentally unsafe.

“There was a vicious circle where fear, frustration and boredom increased the demand for drugs, which in turn fuelled the violence, and thus completed the circle.”

He said there were “many good things” being delivered by dedicated and skilful staff, including health care, education, training and offender management.

“Sadly, Onley will fail to fulfil its role as a training and resettlement prison until it can deal with the inextricably linked blights of drugs and violence,” Mr Clarke added.

Michael Spurr, chief executive of HM Prison and Probation Service, said: “Tackling drugs and violence at Onley is our top priority and, while challenging, significant efforts have been made to drive improvement.

“These have included a major recruitment drive, with 30% more officers soon to be in place compared to 2018, along with additional security measures such as mail scanners, while a new drug recovery unit is due to open this spring.

“As the chief inspector makes clear, despite the difficulties there is good work going on at Onley to help prisoners turn their lives around and reduce the risk of reoffending on release.”

HMP Onley is a training and resettlement prison for men. It held 738 inmates at the time of the inspection.