The national average daily cost of keeping an inmate at an Australian prison has fallen to its lowest level in five years, a report says.

Australia’s prisoner population is costing the country less now than at any time in the past five years but on a daily basis per inmate, it’s still more expensive than a night in a city hotel room.

Data from a new Productivity Commission report into Australia’s justice system shows the national average cost in 2012-13 for an inmate was $221.92 a day.

Across states and territories the cost varies, from $188.82 a day in NSW to $321.24 in Tasmania.

The Tasmanian government said of its corrections operations during the period that there was a change of prison director, with the state’s inmate population peaking at 507 in the summer of 2012.

The report shows that for the 12-month period there was an average of 30,082 prisoners spread across 113 custodial facilities in Australia, a population increase of about 3 per cent from 2011-12.

Despite the increased population, the national average cost for each prisoner was less about $8 a day.

Online accommodation websites show mid-range capital city hotel rooms available for $200 a night.

On average, there was one prison guard for every 22 offenders. In Queensland there was a guard for every 35 inmates, and in WA one for every 15.

On a policing front the Productivity Commission found the cost of state and territory forces equated to $416 for each Australian resident (22.7 million) during 2012-13.

NSW Police had the greatest overall annual operating cost of more than $3 billion, which provided 17,272 operational officers, or 235 for 100,000 people.

Northern Territory Police cost $276 million for the year, with 1651 operational officers, making it the most costly force per capita at $1166.

The Territory government said that during the reporting period the force took on 184 recruits and added an additional assistant commissioner position along with implementing “numerous operational and corporate initiatives to meet its primary policing objectives”.