Inmates have effectively taken control at a violent, overcrowded and vermin-infested jail, a watchdog report has warned.

Chief Inspector of Prisons Peter Clarke raised the alarm over the potential for a “complete breakdown” in order and discipline at HMP Bedford.

Pressing the Government to take urgent action, he said a recent inspection of the prison had revealed a “dangerous lack of control”.

Mr Clarke’s assessment, sent to Justice Secretary David Gauke on Thursday, detailed how “extremely inexperienced” staff struggled to exert their authority.

Prisoners regularly and blatantly ignored rules and staff instructions, often without sanction or challenge.

Mr Clarke said: “Despite the best efforts of staff at all levels, there was a dangerous lack of control in many parts of the prison, leading us to fear that there could all too easily be a complete breakdown in order and discipline.

“At times it felt as if prisoners were effectively in control, choosing when or if to comply with directions and consent to authority.”

On one occasion during the visit, an inspector found prisoners throwing food from higher landings.

Mr Clarke said: “Prisoners’ behaviour was very rowdy and unrestrained and the incident had the potential to escalate.

“Staff were unwilling to go upstairs to intervene, and prisoners told the inspector this was not unusual.”

Mr Clarke triggered the “urgent notification” scheme, which means the Government must respond within a month to set out its response to the findings.

The inspection at HMP Bedford, which concluded last week, found:

– Assaults on staff had risen dramatically, with the rate – 116 in the last six months – the highest in the country;

– There had been five self-inflicted deaths since the last inspection;

– The smell of cannabis and other drugs being smoked “pervaded” some of the wings;

– Living conditions were poor, often overcrowded, dirty and vermin-infested.

It emerged in May that HMP Bedford had been placed into “special measures” after the Prison Service determined it needed additional, specialist support to improve performance.

In November 2016, the facility for adult male inmates was hit by a major disturbance, which reportedly caused £1 million of damage.

Bedford is the fourth jail to be subject to a notice under the urgent notification scheme since it was introduced less than a year ago.

Last month, Mr Clarke triggered the process as he published a scathing assessment of HMP Birmingham.

Mark Day, of the Prison Reform Trust, said: “This fourth urgent notification issued against a local prison since January this year should be a wake-up call to ministers.

“The Chief Inspector highlights an unchecked decline in standards over the space of nine years and so no-one can say that they didn’t see this coming.”

Prisons minister Rory Stewart said: “Bedford prison faces serious challenges. We placed it in special measures before the inspection was conducted and we are bringing in senior experienced managers.

“Our focus will be on reducing violence and drugs along with supporting our prison officers to turn Bedford around. It is abundantly clear that further action is needed.”