A report into standards at Gloucester Prison has described levels of organised activities for inmates such as training and education as "woeful".
The prison has "stable consistent management"
The document, by the Inspector of Prisons, also said one wing of the 18th Century jail should be refurbished.
The prison was described as "very positive" overall because of good management.
Governor Mike Bolton said only more investment would allow him to improve on the inspection's recommendations.
Geoff Dobson, deputy director of the Prison Reform Trust, said: "The report by Anne Owers stands out from other recent inspections of overcrowded local prisons as one that is, with the exception of purposeful activity, very positive.
"The distinguishing factor seems to be stable consistent management from having the same governing governor for over six years.
"This contrasts sharply with the average tenure for governing governors in an establishment, which is 21 months."