PRISON guards at Gatton's multi-million dollar South Queensland Correctional Precinct are becoming increasingly worried for their safety as the facility nears capacity.
The $485 million facility, operated by multi-national company Serco, opened late 2011 with its capacity set at 350 as the world's most high-tech prison.
This week the prison housed 342 - just eight shy of capacity.
United Voice Prison Services co-ordinator Michael Clifford said union officials had heard concerns of inadequate coverage when officers were absent.
"Prison management have failed to consistently provide appropriate relief for staff absences and this raises significant concerns about officers' safety," he said.
Mr Clifford said the concerns would form the basis of a new enterprise agreement now under negotiation with Southern Queensland Correctional Centre.
"We hope that through these negotiations, we can achieve the right staffing arrangements to address our members' about their safety and well-being."
A Serco spokesman said additional staff had been placed for the growing numbers.
"We have recently placed additional staff to manage additional prisoners at Southern Queensland Correctional Centre and are satisfied that meets safety and security requirements," the spokesman said.
"We consistently ensure that we have an appropriate number of staff to run the prison safely and securely. Where necessary, we deploy additional staff."
Serco would not disclose how many officers were on duty each shift.
A Department of Community Safety spokesman said the centre provided secure placement accommodation for sentenced mainstream male prisoners, currently had 300 cells, but had the capacity to house up to 350 prisoners comfortably.
"The additional prisoners are predominantly accommodated in common areas and residential units throughout the prison on 'trundle-style' beds," the spokesman said.