Community and Public Sector Union secretary Tom Lynch says more than 100 staff are unable to work because of injuries or illnesses related to their work.

"As a result of staff shortages caused by the number of officers unavailable for work, and because government policies have resulted in a record number of inmates behind bars, prison management has implemented rolling lock-downs for much of the last 18 months," Mr Lynch said.

"The government trumpets the number of correctional officers it has recruited but it doesn't talk about the fact that nearly as many officers have left the service, so there are still too few officers available to operate the prison safely - hence the lock-downs.

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"Understandably inmates don't like being confined to their cells all day and that can impact their behaviour when they are unlocked. This also adds to the pressure officers face going about their normal work."

A government spokeswoman said since May 2016 the government had recruited an extra 94 correctional officers, with further recruitment currently underway.

"As recently as last week, unions have been directly responsible for lock downs with their own stop work action," she said,

"There are currently about 7 per cent of Tasmania Prison Service correctional officers off work for a variety of reasons.

"This figure has remained consistent over the past few years and is in addition to a number of staff on return-to-work programs.

"Lock-downs vary in length, and do not necessarily involve the whole prison complex but may be limited to a single unit, and they can occur for a number of reasons, some of which are beyond the control of TPS staff.

"They are an essential operational tool, utilised to ensure a safe and secure prison environment for prisoners, staff and visitors."

Mr Lynch said with a new prison and remand centre soon to be built in the North, hundreds of extra correctional officers will need to be recruited over the next five years.

"Prison populations are expanding in every Australian state and new prisons are being built so demand for correctional officers is likely to see Tasmanian officers move interstate, particularly as we have the lowest salaries for experienced officers," he said.

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