He has also suggested the Liberal Party might be filling the social policy gap, returning to the days of Kate Carnell's small 'l' liberalism with the election of Elizabeth Lee as the party leader.

Mr Stanhope, who was the chief minister from 2001 to 2011, turns 70 on Thursday.

An interview with The Canberra Times to mark the milestone quickly turned to his criticism of the Barr Labor-Greens government and particularly the "failure" of the Alexander Maconochie Centre, the ACT's $130 million jail which opened in Hume in 2008 under his leadership.

When he was chief minister, Mr Stanhope said the the jail was "one of the great achievements of this government" and reckoned the Liberal opposition "did not have the guts to build a prison".

More than a decade late, he has changed his tune, claiming the jail does not live up to the hype of being human rights-compliant and has not done anything to prevent released prisoners from reoffending.

"I must say I increasingly feel my passion for the ACT to have its own prison, in retrospect, was a mistake," Mr Stanhope said.

It would have been better not to have built the jail, he suggested. "It is, on reflection, hard not to think that. To date it's been an appalling failure. It's an embarrassment," he said.

Mr Stanhope said there was "nothing to do" in the jail.

"[That is] compounded by the fact our rhetoric is so strongly around it being a human rights-compliant prison and rehabilitation is the focus, when the truth is the reverse," he said.

The Canberra prison population has continued to rise, from 268 detainees in 2012 to 429 in 2019. It climbed to as high as 507 detainees in 2018.

Former Corrections Minister Shane Rattenbury oversaw the government's pledge to spend $132 million to reduce recidivism - or reoffending - by 25 per cent by 2025. Three-quarters (77 per cent) of the ACT's detainees have previously been sentenced to prison, while the national average is 58 per cent.

The prison has also experienced riots, cost blow-outs, lockdowns, overcrowding, too few prison officers and serious allegations of abuse, including by an Aboriginal woman on remand who said she was strip-searched in front of male prisoners.

Mr Rattenbury, now the ACT attorney-general, said he spent his eight years as corrections minister trying to fix the jail.

"The fact is, the ACT Government has faced significant challenges stemming from the AMC's original design," Mr Rattenbury said.

"For example, the AMC was built without enough accommodation space, it did not support prison industries, it did not have facilities for recreation or worship, and it did not have a defined human rights framework. It was opened without a needle and syringe program or a dedicated Aboriginal health service.

"As corrections minister, I spent my entire tenure trying to turn this around. We now have an expanded range of employment opportunities, including the AMC Bakery providing hospitality training for detainees to help them gain skills and experience.

"We have expanded accommodation to meet growing demand and planned a Reintegration Centre to help ease detainees transition back to life on the outside. Winnunga Nimmityjah operates inside the AMC, the only jail in Australia that has such a model."

The new Corrections Minister Mick Gentleman said now was the time to look forward.

"We know parts of the Alexander Maconochie Centre are not operating how they were originally intended. I've made it clear that reform and improvements are at the top of the agenda for Corrections in the ACT. Now is the time to look forward and work with staff, stakeholders and detainees on solutions," Mr Gentleman said.

"Housing maximum security, minimum security and remand detainees at the Alexander Maconochie Centre presents unique challenges. A higher than anticipated number of more serious offenders and higher security detainees has created accommodation pressures. We are considering a range of options and investments to better meet accommodation needs of the AMC, particularly for female detainees.

Mr Gentleman said the government was "committed to reducing the overrepresentation of Aboriginal and Torres Strait Islander people in the justice system".

"We are supporting our Aboriginal and Torres Strait Islander community to determine a pathway forward and I look forward to hearing from them on these important issues," he said.

Mr Stanhope's view on the jail have been informed by his current role as a senior advisor to the Winnunga Nimmityjah Aboriginal health service in Narrabundah.

In the ACT, Aboriginal and Torres Strait Islander adults make up 1.9 per cent of the ACT population and 22 per cent of the ACT prison population.

Mr Stanhope said speaking to clients of Winnunga Nimmityjah who had been in jail, some in a number of jurisdictions, he always asked them where they would have preferred to be imprisoned. None have ever said the Canberra jail. That was despite one of the jail's aims being to help prisoners keep in contact with family in the ACT.

"They say the NSW system is far better, the Queensland system is better, and I find that shocking," he said.

When asked what was so wrong with the AMC, Mr Stanhope answered: "The fact that there is nothing to do.

"[That is] compounded by the fact our rhetoric is so strongly around it being a human rights-compliant prison and rehabilitation is the focus, when the truth is the reverse," he said.

"So we have this pushed down people's throats - 'Oh human rights, we're concerned about you, we're trying to reduce recividism, we're trying to rehabilitate you'.

"As far as the Aboriginal population is concerned, we have the highest rate of Aboriginal incarceration in Australia, we have the highest Aboriginal recidivism in Australia. So it doesn't work. Whatever it is we're doing is clearly not working.

"These numbers are staggering. The rate of imprisonment of Aboriginal people in the ACT has grown by 279 per cent in the last 10 years against the national average of 48 per cent."

Mr Stanhope said he personally knew the Aboriginal woman who alleged she was strip-searched in front of males at the jail and was shocked by Labor and the Greens' response to her claims, which he suggested was part of a changing dynamic in the Assembly.

Earlier this year, Labor and the Greens reject a push by the Canberra Liberals for an independent investigation into the prevalence of racism at the Alexander Maconochie Centre.

Mr Stanhope said he was dumbfounded by that development.

"[The woman] in her claims around the incident claims they were infected around systemic and institutional racism and for the Labor Party and the Greens to dismiss that and for the Liberals to then pick it up and say, 'Well, I think we need to have a look at this' and for the Greens and Labor to vote that down is an interesting sign that things are changing in terms of the dynamic in the Assembly," he said.

Mr Stanhope said he believed the Canberra Liberals were returning to the small 'l' liberalism of former Liberal chief minister Kate Carnell with the election of Elizabeth Lee to lead the party.

"I think it's been obvious to everyone in Canberra that this community is just not going to support a deeply conservative or socially conservative government. I think the Liberals have finally awoken to that," he said.

By contrast, he believed Labor and the Greens were leaving their traditional supporters behind, claiming the government was not doing enough to support issues such as affordable housing.

"I would say the government simply has a different set of priorities than those I believe should be the priorities of a Labor government," he said.

What does he think the government's priorities are?

"I'm not entirely sure," he said.

"I have trouble working out where the money's going but I can tell you where the money's not going - it's not going into the public and the money is not going into affordable housing or social housing, it's just not, the evidence is clear."

Mr Stanhope said he did not believe the government understood "the impact of some of their policies on some of the most needy people in this community".

"My concern is there are some aspects of governance here in the ACT , most particularly those that disproportionately affect people in the lower two percentiles. They have been forgotten and that's an issue I believe the Labor Party and the Greens need to own and address," he said.

Chief Minister Andrew Barr rejected Mr Stanhope's assessment.

"I wish Mr Stanhope a happy 70th birthday. He made a significant contribution to Canberra during his decade in office," Mr Barr said.

"Housing affordability is a challenge for all Australian states and territories at this time given prevailing economic conditions such as record low interest rates, closed international borders and taxation policy settings at a national level.

"Undoubtedly, increased supply of housing is a priority and more dwelling sites have been released to the market in the past six years than the entirety of Mr Stanhope's decade as chief minister."

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