Inmates at a Kent youth prison spend far too much time in their cells because of staff shortages, according to a new report.

The Independent Monitoring Board (IMB) annual reports says fewer prison officers at Cookham Wood Young Offenders Institution mean boys are being cooped up for too long, and that frequent, unpredictable restrictions on their activities are “inhumane”.

The establishment, in Sir Evelyn Road, Rochester, houses up to 188 inmates aged 15 to 18, from all over southern England.

Monitoring board members say that for the past year, it has been operating with up to 20% fewer prison officers than authorised and recommended.

Because of this, there have been regular but unpredictable restrictions of the boys’ activities for safety reasons.

At the worst point, in June, a typical inmate at the site had only five hours out of his cell on weekdays, and only two hours a day at weekends.

There were regular education shutdowns, restrictions on social time, and many boys missed appointments because officers could not be freed to accompany them.

At the same time, there was a high level of violence, with 14 assaults on staff in June. The IMB argues that frustrations at the restrictions fuelled violence within the establishment.

Anne Finlayson, chairman of the board, which is made up of unpaid volunteers from the nearby community, said: “It is hugely frustrating, there are so many good things about Cookham Wood.

“The staff are caring and fair.

“Education and healthcare are excellent and there are many counsellors and trainers to help the boys turn their lives around.

“There are simply not enough officers to give the boys the access they need to what is on offer.”

Ms Finlayson also said The Ministry of Justice had authorised a vigorous campaign to recruit more officers at the institution.