Overcrowding is highlighted as a major issue in a report into a County Durham prison.
The report follows an unannounced visit to the prison in August
The report by chief inspector of prisons, Anne Owers, says male inmates at Durham Prison are missing out on education and work opportunities.
But she said relationships between staff and prisoners are good and the unit provides a "safe and decent environment".
Ms Owers said: "Durham men's prison is operating under great population pressure.
"Unusually, it is also running an integrated regime, without separating out vulnerable prisoners, including sex offenders.
"This inspection found that nevertheless it was a safe prison and the need to ensure the protection of vulnerable prisoners appeared to make staff more alert to the safety of all prisoners."
The report follows an unannounced inspection of the men's section of the prison, where there are around 580 inmates, in August last year.
Ms Owers said Durham provided a "fundamentally safe and decent environment" and praised the commitment and professionalism of staff.
But she said: "However, it is also clear what it was not able to do: to provide an environment where prisoners could acquire new skills and be assisted into the employment and lifestyle that might prevent them returning in very short order."
They found the prison was offering too little "purposeful activity" with spaces for only one in 10 of the prisoners who needed basic literacy and numeracy skills, no accredited training and around half of the prisoners had no access to jobs or education.
The report said reception, suicide and self-harm and anti-bullying work were all of a high standard.
It said relationships between staff and prisoners were "consistently good" and most of the recommendations from the last report had been exceeded.
The inspectors said prisoners were not out of their cells often enough, although they were out regularly.
It also said there were five incidents when staff saved prisoners after suicide attempts.
Director general of the Prison Service Phil Wheatley said: "I am pleased that the chief inspector recognises the achievements of the staff at Durham in the face of current population pressures.
"I acknowledge the chief inspector's concerns regarding work and education provision.
"The Governor and staff are working to improve provision both by introducing part-time work and education and by opening new classrooms and an educational assessment centre in 2004."