PRISON officer numbers are at such a low level that prison unrest, assaults on staff and self-harm rates are soaring, a charity claimed last night.

The Howard League for Penal Reform said falling officer numbers in public sector prisons – due in part to austerity measures, and more recently by recruitment difficulties – were leading to safety in jails deteriorating "significantly".

Deaths in prison, prisoner suicides and attacks on inmates were on the increase, fuelled by the falling frontline officer numbers.

High security Frankland Prison in Durham – where Yorkshire Ripper Peter Sutcliffe was transferred last month – saw assaults on prisoners increase almost four-fold towards the end of last year and early this year, with the prison told to take "prompt action" to tackle the issue.

At Holme House Prison in Stockton, violent incidents increased by 60 per cent between 2014 and 2015.

And last year a riot at Deerbolt Young Offenders' Institution, near Barnard Castle, saw inmates out of the control of prison authorities for several hours, with fires started in some cells and prison officers being forced to retreat under a hail of pool balls and other weaponry.

Durham Prison, which should hold no more than 595 inmates, was significantly overcrowded, averaging 930 earlier this year – but prison officer numbers there dropped by 31 since 2013.

Terry Fullerton, North-East representative of the Prison Officers' Association, said: "Murders in prisons, serious assaults on staff, self harm, suicides and assaults on prisoners have all increased across the country.

"A safe prison is one that is well-staffed, that is the top and bottom of it.

"The morale among officers is pretty low. Prisons are more violent places to work, and they are not recruiting at the levels they need to to replace people leaving.

"The nature of the job and levels of violence inside prisons are putting people off becoming officers."

Mark Fairhurst, on the executive committee of the Prison Officers' Association, added: "The ever-increasing violence and the lack of support from management when staff defend themselves from violence all add to the realities of a service that is clearly in crisis.

"In an area like the North-East where public sector work contributes to communities it is shocking that people choose not to pursue a career in the prison service.

"Our employer needs to start recognising the difficult and brave work our members do on behalf of society and show appreciation in the form of appropriate remuneration to attract and retain staff."

He said despite extra recruitment, it was not keeping up with the numbers of officers leaving the prison service.

A Ministry of Justice spokesperson said: "Safe prisons are fundamental to the proper functioning of our justice system.

"Our dedicated prison staff, who support tens of thousands of prisoners every day, are vital to the safe running of our prisons. We have recruited 2,900 staff over the last 12 months and are taking significant action to make sure we have appropriate staffing levels.

"The Secretary of State is determined to make sure our prisons are safe and places of rehabilitation and will set out her plans for reform shortly."