Staffing levels have become "unsafe" at a prison which was hit by large-scale rioting 12 years ago, inspectors have said.

Bosses at Manchester Prison - formerly known as Strangeways - have been warned more staff are needed after they cut 30% of the workforce to save money.

Some prisoners at the jail were also kept in "degrading" conditions, said the chief inspector of prisons, Anne Owers, in a report.

It is possible that staffing levels have been lowered to the extent that they are unsafe

Anne Owers, Chief Inspector of Prisons

She also said the prison was still scarred by the memory of the 1990 riots, in which two people died and damage costing over �60m was caused.

Overcrowding had resulted in "degrading" conditions where some prisoners had to share one-man cells fitted with unscreened toilets, Ms Owers said in her report.

Conditions were likely to have got worse as a result of a rising prison population since the inspection last November, she added.

Self harm

The number of prisoners being assaulted or who were self-harming had also raised concerns over the safety of inmates and staff at the jail.

Ms Owers concluded: "It is possible that staffing levels have been lowered to the extent that they are unsafe.

Rioters caused �60m damage in 1990

"We believe that Prison Service headquarters should review the staffing profiles to ensure that all work is identified and resourced so that prisoners and staff are not put at risk."

The prison was also criticised for keeping severely mentally ill patients in the healthcare centre rather than in secure hospitals.

However, inspectors were impressed with the "can do" attitude of management and staff.

Staff who worked in their own time to improve ways of tackling the prison's high suicide and self-harm rates were also praised.

Prison Service director general Martin Narey said he shared concerns over overcrowding.

He insisted however, the prison is "highly efficient".