The ACT government confirmed guards intervened in a "physical altercation between two detainees" on New Year's Eve.

The Canberra Times understands the remandee involved needed stitches for deep cuts to his skull inflicted by a sentenced prisoner. But a Corrections spokeswoman said both men's injuries were deemed to be minor and treated on site.

The 2019 report on government services found there were 2.32 serious assaults for every 100 prisoners in the ACT during 2017-18, down from 3.59 the year before.

Only Queensland, with a prison population 17 times that of the ACT's, had a worse rate for serious assaults during 2017-18 at 2.94 per 100 prisoners, though the threshold for reporting such incidents varies between jurisdictions.

Serious assaults are defined as "acts of violence resulting in injuries that require treatment involving overnight hospitalisation ... or ongoing medical treatment, as well as all sexual assaults".

Assaults overall rose to 16.02 per 100 prisoners and have remained high for the past four years.

While the government did not provide detail about assaults in 2019, a spokeswoman said the prison had handed over CCTV footage of the New Year's Eve incident to police and would undertake its own internal review.

In response to recommendations from a 2016 inquiry into the death of Steven Freeman, a remandee who was once bashed within hours of his arrival at the jail, the government has installed about 80 extra CCTV cameras across the prison and strengthened its relationship with police in prosecuting assaults.

The new memorandum of understanding between the agencies had already led to a number of prosecutions, Corrections Minister Shane Rattenbury said, and sent a clear signal that attacks would have consequences.

But the government has ruled out building a separate remand centre, another key recommendation of the review, which urged it would help ensure "greater human rights compliance" at the prison.

Mr Rattenbury said it would cost hundreds of millions of dollars to build a specialised facility when other concerns such as capacity and keeping people out of prison in the first place took priority.

"Of all the things we need to work on, I don't think a remand centre is the most pressing thing on my list," he said.

Overcrowding has been a near-constant issue at the prison since it began taking inmates in 2009, despite an expansion in 2016, with two detainees now crammed into nine-square-metre cells designed for one, and multiple sources confirming remandees are routinely bunking with sentenced prisoners.

A record 507 prisoners were locked up at AMC in June last year, four inmates shy of capacity.

As of January 25, 2019, 484 prisoners were on site. Of these, 38 per cent were being held on remand waiting for their case to be heard, or waiting to be sentenced.

A government spokeswoman said detainees could be "relocated at any time as part of usual procedures to ensure the safety and security" of the prison but did not provide figures on how many remandees were accommodated with convicted prisoners.

ACT Human Rights Commissioner Helen Watchirs said she had reminded the government that, under the law, remandees and sentenced detainees should only be housed together in exceptional circumstances such as an issue of safety.

The commission said this right to separation reflected the presumption of innocence for detainees who have been remanded in custody but not found guilty of an offence, and protected them from the risks posed by sentenced prisoners, who could be locked up for violent offences.

The commission was also closely monitoring general overcrowding at the prison, Dr Watchirs said, though it had not yet become an "inhumane or critical issue".

At Legal Aid, Jane Campbell said it appeared the right to separation hadn't been tested in court before.

A government spokeswoman said ACT Corrective Services agreed with a separation policy "where practicable and in the best interests of individuals".

But in a small jurisdiction where both male and female prisoners with multiple security classifications were housed in the one prison, issues preventing separation such as existing grievances and debts between detainees were especially tricky to navigate, she said.

There were also circumstances when the "temporary placement of remand and sentenced detainees [together] may be beneficial for individuals for cultural, religious or other reasons", the spokeswoman said.

New admissions to the jail are now placed under observation in a separate cell block for their first five to seven days.

On Wednesday the government released a clear set of human rights principles to "formally clarify" how prisoners should be supported by corrections, from arrest to release.

A spokeswoman confirmed the principles of legislation, which will be distributed widely to ACT prisoners and postered around the jail, had not been reviewed or changed but rather translated into new practical standards for staff and detainees - a first in an Australian prison.

"The AMC when it was launched was described as being a prison that was aspiring to be a human rights compliant jail and I don’t think anyone ever really actually defined what that meant," Mr Rattenbury said.

"This is about being transparent...and definitive about the standards we're striving to deliver."

While the new principles stress a remandee must be treated in a way appropriate to their status as an unconvicted person, they do not mention the right to separation from sentenced prisoners, as outlined in the ACT Corrections Management Act.

The Canberra Times understands work on major reforms for the ACT justice system is nearing completion, after a forum hosted by the government in December examined rehabilitation programs beyond the prison gates.

It is understood a feasibility study into another expansion at the jail is still being considered by the government and Mr Rattenbury said work was underway "on a response" to the rising numbers of both sentenced prisoners and those on remand across the country.

Neil McAllister, recently installed as the ACT's first prison inspector, is also reviewing conditions for remandees at the prison and has expressed concern that people on remand are being treated like convicted prisoners.

In May last year, an indigenous man on remand was attacked by a sentenced prisoner while housed in the same medium security unit during night-time lockdown. Scalding water was poured over the remandee's head and he was struck by a can concealed in a sock before being rushed to hospital with burns and cuts.

But in reviewing the attack, Mr McAllister found staff could not have foreseen the assault and it was reasonable for the two detainees to be housed together given their extensive criminal histories and involvement in assaults at the prison.

According to the Productivity Commission figures, time spent by inmates out of their cells in the secure part of the ACT jail was just 8.4 hours per day, matching NSW as the lowest in the country against a national average of almost 10 hours.