The BBC's Emma Patterson: "Some prison officers say security is being compromised"

According to the National Audit Office (NAO) the number of officers missing work through illness every day would be enough to staff seven jails. Figures show staff are taking up to16 days sick leave each year.

Now prison officers could be forced to take annual fitness tests in an attempt to cut a sick leave bill of up to �62m.

Emma Paterson: "The prison service may set up an annual fitness test"

Female prison officers averaged 18 days sick leave a year compared with 13 for male officers.

At East Sutton Prison in Maidstone, Kent, officers were taking more than 26 days a year compared with just 2.5 days at Morton Hall in Swinderby, Lincoln.

Stress blamed

The high level of sickness meant 116 out of the 127 prisons in England and Wales were operating at below planned staffing levels, causing serious problems and limiting the amount of time prisoners could spend on purposeful activity.

Injuries account for more than a third of absences and a fifth of time lost was due to stress, anxiety and depression. About 3% of the days lost were due to assaults on staff.

The NAO report said the Prison Service needed to investigate whether "inappropriate management styles" were contributing to work-related stress.

In three prisons, almost 40% of staff said harassment and bullying at work carried out by managers was causing stress.

The report also urged scrutiny of the number of people taking early retirement on health grounds, currently accounting for more than half of all retirements from the Prison Service.