But the former Labor leader said the Alexander Maconochie Centre's capacity problems were not a major roadblock, and called for strong leadership to ensure it becomes a world's best practice, human rights compliant jail.

Mr Stanhope was the driving force behind the construction of the centre, and envisioned the creation of a progressive facility that encouraged rehabilitation and reform. But under his watch, the prison's capacity was reduced from 374 beds to 300 beds.

Speaking on Thursday about the recent revelations on serious prison overcrowding, Mr Stanhope said he stood by his decisions to maintain the jail's $128 million budget.

''I'm prepared to accept my role and responsibility in relation to budget decisions,'' Mr Stanhope said. ''I think if anybody is to be beaten around the head over that, it should be me, as chief minister, and as the person who drove the decision to build a prison here.''

The downsizing of the prison went ahead despite the government having a confidential report, produced by John Walker Crime Trends Analysis, suggesting the prison would need space for 335 inmates by 2009, the year it opened.

Now authorities have been forced to urgently upgrade the prison's capacity to 366 to cope with surging prisoner numbers, which have risen by 40 per cent since January.

Mr Stanhope said the planning of the jail was never ''black and white'', saying there were a range of considerations and projections, including the Walker report, that informed the decision to build the prison to a capacity of 300.

''It's really simple and easy in retrospect to say 'oh, look, you were wrong,' '' he said.

''In an ideal world, if cash or funds were never an issue, we probably would have spent twice as much on the prison.''

He said on Thursday he had held ''very high expectations and hopes'' for the AMC, but maintained it was too early to judge the facility's success, just three years after it began operations.

He said overcrowding presented a direct threat to the ability to rehabilitate the ACT's criminals.

Mr Stanhope, who described himself as a ''very interested observer'', said the prison had faced hiccups in recent years. ''I do have a certain degree, a fairly significant degree of anxiety that the Alexander Maconochie Centre is not being managed as I had hoped it would be.''

The former chief minister accused ACT Corrective Services of never fully embracing the ideals of a human rights compliant prison. He challenged the AMC's leadership to conduct a presentation to the government and the community, to compare its progress against world-leading human rights compliant jails, such as those in Norway.

''I don't think they'll come out of that particularly well, and I think there's no excuse for not coming out of that particularly well,'' he said.

Corrections Minister Shane Rattenbury rejected the claim that ACT Corrective Services were not passionate about human rights compliance. ''Jon is presumably basing his comments on practice during his time as chief minister,'' Mr Rattenbury said.

''However, since he left the assembly in 2011, there have been substantial staffing changes, in particular new management.''

Mr Rattenbury accepted Mr Stanhope's claim that the overcrowding did pose a risk for human rights compliance and rehabilitation at the prison.

But he said the situation was being closely monitored on a day-to-day basis to ensure the pressures were dealt with.