Prison staff are being accused of corruption, bringing in contraband, and having inappropriate relationships with inmates.
Figures released to 1 NEWS under the Official Information Act reveal Corrections have investigated 387 claims against staff in the 2019/2020 year.
One-hundred-and-twenty-five investigations are related to careless or unsafe behaviour, 116 for inappropriate relationships, 77 for misusing information, and 3 are for corruption.
Corrections Association spokesman Paul Dennehy told 1 NEWS that the incidents should be taken seriously.
"It could be … a staff member who is abusing their position either sexually or racially or using excessive force," Dennehy said.
But the overall number has dropped by 135 in five years, when 522 investigations were carried out in 2015/16.
In a statement, Corrections pointed to pre-employment checks, a new integrity committee and a staff teaching programme, to prevent harm.
Dennehy said the 10-week training programme staff undertake isn’t enough.
"There’s not enough time spent on the basics of doing the job properly and safely, and we've raised that as an issue with the department," Dennehy said.
A inside source told 1 NEWS the numbers are unreliable.
"Prison managers can decide whether issues should be officially reported or not and some Managers under-report (to preserve their reputation), while some can be pretty zealous," the source said.
A Corrections spokesperson said it expects the utmost professionalism and allegations are taken seriously.
Of the 387 staff investigated, 40 quit or were dismissed. The others are still on the job.