Canberrans are being jailed at the highest rate in a decade and the ACT has the worst proportion of prisoners who have spent previous time behind bars in Australia, new prison data has revealed.
The Australian Bureau of Statistics' annual report into prisons showed the territory's jail population hit 130 inmates per 100,000 adults at the end of June, which was its highest rate since 2004.
It reflected a nationwide upswing as imprisonment rates reached 10-year peaks in all jurisdictions except NSW and Tasmania this year.
Australia's overall prison population of 33,791 was also the highest in a decade and came on the back of the biggest annual jump in prisoner numbers since 2004.
The report showed 77 per cent of ACT inmates had spent time in jail before, which was above the national average of 59 per cent and the highest percentage of repeat offenders of any state or territory.
The latest figures highlighted the worsening problem the ACT Government faces as the territory's overcrowded jail continues to buckle under the strain of an unprecedented surge in detainees.
Opposition corrections spokesman Andrew Wall said any further increase in prisoners would only place additional pressure on the Alexander Maconochie Centre.
He said planned upgrades to Hume facility would only serve as a "stop-gap" if inmate numbers continued on an upward trajectory.
Corrections Minister Shane Rattenbury said the ACT Government had taken a two-pronged approach by expanding the territory's overburdened prison and funding programs to help slash offending rates.
A planned $54 million upgrade to the Alexander Maconochie Centre to help ease overcrowding issues would add 110 beds to the Hume facility by mid-2016.
Mr Wall said the jail would be further strained by the government's plans to abolish periodic detention by 2016-17, a move which would limit sentencing options in the ACT to either a custodial sentence or community-based orders.
"Twenty-two per cent of the ACT's prison population is made up of un-sentenced prisoners, which goes against world best-practice for sentencing offenders."
The government committed more than $2 million in this year's budget to continue its fledgling Throughcare program, a community-based initiative designed to keep offenders out of jail.
The release program focuses on housing, health, income and basic life skills and Mr Rattenbury said early outcomes were positive.
"In the 2013/14 financial year there were 229 releases to the Throughcare program.
"Of these, only 34 returned to custody, 24 for breach of parole or good behaviour orders and the remainder as the result of new offences.
"Our recidivism figures are high but this reflects the fact that the ACT has a relatively low incarceration rate and that those sent to prison in the ACT typically have more endemic offending problems," Mr Rattenbury said.
Mr Wall said it was too early to measure the Throughcare program's long-term effectiveness.
"But we're still taking about 77 per cent of the ACT's prison population being frequent flyers," he said.
ACT criminologist David Biles didn't view the territory's high rate of prisoners who had spent previous time in jail as "necessarily a bad thing" and said those figures were less important than the overall imprisonment rate.
"There are two types of people I want to see in prison. One is very serious offenders such as murderers and rapists who haven't committed any previous offences but who have to go to jail because of the seriousness of the offence.
"The other is repeat offenders, people who keep breaking into houses, keep stealing cars or supplying drugs. They're the people who need to go to jail."
Dr Biles said it was a shame the territory no longer had Australia's lowest rate of imprisonment, which now belonged to Tasmania with a rate of 112 inmates per 100,000 adults.
"It's very hard in small jurisdictions, you get three or four very serious cases, which we have had, and that pushes it up because [the offenders] stay in jail for years," Dr Biles said.
Men made up 94 per cent of inmates in the ACT and 16 per cent of prisoners were Aboriginal or Torres Strait Islander.
The report showed 22 per cent of prisoners had not yet been sentenced, which was below the national average of 24 per cent.