THE 110 prison officers at Scotland's most overcrowded jail yesterday refused to work overtime in a bid to highlight staff shortages. Their action came as it was revealed that Craiginches Prison, Aberdeen, was so full that one-man cells were being used to house as many as four prisoners.

A Scottish Prison Service spokesman said: ''We do concede that this is not an ideal situation. We are just not allowed to turn prisoners away. But it causes no threat to anyone. The prison service have made contingency plans for this kind of situation and in no way will security be jeopardised.

''We should be able to cope as long as there is not an increase in officers going on sick leave. It is not a dispute between staff and management. It is merely the officers deciding to work their contracted hours, which they are perfectly entitled to do.

''They are contracted to work 78 hours in a two-week period and the move not to do any overtime has stemmed from the fact that officers have not been getting time they are owed.''

The prison is currently 68% over-occupied, with 215 prisoners living in space for 128.

Fears that overcrowding and understaffing could lead to safety risks increased last month when officer Mark Askew allegedly had his throat slashed by an inmate.

Mr Jim Dawson, deputy general secretary of the Scottish Association of Prison Officers, said: ''We fully support the decision taken by the Aberdeen branch. Our members for some time now have been working under intolerable pressures at Craiginches.

''The staff have accumulated thousands of hours owed them in lieu, but there is no chance that they will be able to take them.''

Three officers from other prisons have been drafted in as a temporary measure to help alleviate the situation. Six additional officers will also be starting work at the prison as from June 22.

Building work at Craiginches is expected to make space for another 15 inmates by the end of the year.