ACT Corrections Minister Shane Rattenbury is calling an urgent ministerial roundtable to find a solution to overcrowding at Canberra's jail.

There has been a 40 per cent increase in the number of prisoners at the Alexander Maconochie Centre since January.

Mr Rattenbury says the increase is unprecedented and has pushed the prison close to capacity.

"The pressure is so great on the prison at the moment that we need to take serious steps," he said.

"I want to bring the key stakeholders together so that the leaders in the sector can have a serious conversation about what's driving the increase in prison population and what responses we might take both in the short-term but of course in the longer term as well."