Inspectors have warned a Suffolk prison might face disciplinary problems with inmates if the regime does not improve.
An Independent Monitoring Board report on Highpoint Prison, with 816 inmates at Stradishall, said staffing was too low and it had too few resources.
Inspectors identified problems a second time - it was criticised in 2005.
Accommodation is described as unfit for purpose in a report that also reveals a lack of training opportunities for inmates and low morale among staff.
The report warns if there is no improvement there could be "concerted indiscipline on the part of the prisoners".
An investigation by the independent board in 2005 revealed that too many inmates were forced to share a cell and healthcare was not up to standard.
Their report said sharing single cells was degrading for inmates and unacceptable.
The Prison Service said in a statement: "Highpoint prison is currently in the middle of a recruitment campaign, and five successful candidates have already been identified and the process is ongoing.
"The governor at Highpoint and her senior management team have focussed a significant amount of time on the issue of staff sickness and while improvements still need to be made, the prison did meet its target to ensure less than 12.4 days sickness leave was taken per member of staff in 2006/07 with an outturn of 11.5 days."