Gartree Prison 'unsafe because of staff shortages'
A prison which holds large numbers of high-risk inmates serving life sentences is "no longer safe enough", a report has found.
Inspectors said HMP Gartree in Leicestershire had declined from "safe and stable" to a prison which had "lost its way".
HM Inspectorate of Prisons put much of the blame on staff shortages and a changing prison population.
The Prison Service said increased staffing would drive improvements.
Gartree holds more than 700 inmates, all serving indeterminate - mostly life - sentences, most of who pose a "high risk of harm to others".
An inspection in November found a shift in prisoner population from those near the end of their basic tariff to those more recently sentenced.
The report said: "The stability we have praised in the past had been undermined by staff shortages that seemed to impact on nearly all aspects of prison life.
"This was evidenced by managerial drift and by delays in fully coming to terms with the challenges posed by a changing population."
Levels of violence and victimisation had also increased and it was now in line with national averages, the report said.
Noting Gartree holds "very challenging prisoners", the inspectors found incidents of self-harm had quadrupled.
However, they said public protection was a high priority and well managed.
Michael Spurr, chief executive of HM Prison and Probation Service, said: "HMP Gartree will use the recommendations in this report to drive progress over the coming months.
"Staffing numbers are being increased to provide an improved regime with more training and activity opportunities for prisoners."