A report says Stocken Prison is operating reasonably successfully but needs to provide more work, training and education for its prisoners.
An announced inspection was carried out at the prison, which has more than 1,000 prisoners and is a training jail.
Its last inspection in 2010 said it was reasonably safe but failing to provide activity of sufficient quality.
This follow-up inspection found evidence of improvements and inspectors were pleased to find the prison was safe, has adopted a robust approach to anti-social behaviour, is bright and clean and that relationships between staff and prisoners had improved.
It also said health care had significantly improved.
But inspectors were concerned that activity places had not grown with the population of the prison and that the treatment of vulnerable prisoners required improvement.
Chief inspector of prisons Nick Hardwick said: “Overall this is a reasonably good report. Stocken is a surprisingly large prison and a significant management challenge. Progress had been made in all areas but more needed to be done to provide sufficient activity.”
A copy of the full report can be found by visiting www.justice.gov.uk