And prison officers will not let them out of the cells until the Department of Corrective Services tells them about its plans to increase the number of inmates at the facility.

The industrial action follows the Department’s plan to increase the number of inmates the jail can accommodate from 500 to 600.

But staff are concerned the Department has not given any indication about increases to employee numbers to cope with the extra 100 inmates.

According to sources at the jail, bunk beds are already there, waiting to be installed into the cells.

Matt Bindley, chairman of the Prison Officers Vocational Branch, yesterday confirmed the plan was to leave the prisoners locked in their cells until the Department speaks to them.

Mr Bindley has been negotiating with the Department over the increase.

A spokesman for the Department of Corrective Services said the only time prisoners would be let out would be for court or bail hearings, or if they are due for release.

Originally opened to house 300 inmates in July 2004, the jail near Kempsey was later restructured to increase the number of inmates it could hold to 500.

But with more people in NSW jails than ever before the local jail is one the Department of Corrective Services is looking at to increase capacity.