Almost double the amount of new beds allocated in this year's Budget is needed to manage the prison population, corrections workers say.
The government announced units to house 600 inmates would be built by the end of 2019.
But, Public Service Association national organiser Willie Cochrane said that was not enough.
"The whole Corrections Department has always been a political football and the sooner we start having conversations about what's best for people without politicising it."
The association was "deeply concerned" about the number of beds the government had offered.
"We've had quite a large muster build up over the last two or three years and we are struggling to keep up with prisoner accommodation. We were looking for some extra capacity to remediate some of the overcrowding issues that we have.
About 1000 beds would have been a better number, Mr Cochrane.
"We're unsure where this government's going to go regarding any legislation around bail laws or what have they got planned for the future so that [number] would have given us a little more breathing room."
The PSA represents 3300 corrections staff across the country.
Mr Cochrane said under the current arrangement there was "absolutely" concern for the physical safety of staff.
"We have been working closely with the Department [of Corrections] in trying to rectify these issues."
Despite a recruitment drive and many new workers joining the role, retention was low because of the pressure, he said.
Workers enjoyed their jobs and wanted to be part of the solution.
"We've made it quite clear that we want some answers, we do want to work with them and we'll support the initiatives but we seriously need to see some movement."