Northern Territory's Police Commissioner has taken the unprecedented step of quitting the NT Police Association after the union criticised his historic apology to Indigenous people at the Garma Festival.

Commissioner Michael Murphy formally apologised over the weekend to all Aboriginal Territorians on behalf of the force, telling the crowd he is "deeply sorry for past harms and injustices caused by members of the Northern Territory police".

"We know that we cannot change or undo the past, but together we can commit to not repeating our mistakes and the injustices," he said.

However, his comments were criticised by the Northern Territory Police Association (NTPA), who released a statement on Sunday in the wake of the Commissioner's apology.

Acting President Lisa Bayliss said while it is important to "confront, acknowledge and learn from the past," it couldn't define the NT Police.

"Our officers are committed to serving the community with integrity, impartiality, and professionalism, treating all individuals with the respect they deserve, regardless of race, gender, or background," she said.

"Over the past 154 years, our membership, both Indigenous and non-Indigenous, have protected the community from domestic violence, alcohol abuse, and other forms of harm.

"It is also not the role of police to assess the success or otherwise of Federal Government-directed policies of Closing the Gap, the Stolen Generation and the Intervention, as the Commissioner has done."

@natindigtimes Northern Territory Police Commissioner Michael Murphy has apologised to Aboriginal Territorians for the "past harms and the injustices caused by members of the NT Police." #aboriginalaustralia #firstnations #aboriginal #indigenous #nt #northernterritory #police ♬ Conspiracy - Kieran Rogers

Ms Bayliss argued Commissioner Murphy didn't communicate the "content, and intent, directly with the membership well in advance of his speech", arguing the media received it beforehand.

"Our members deserve the backing of the senior police executive, ensuring they are not unfairly overburdened with blame but rather empowered to continue their vital work for the benefit of all Territorians," she said.

In response, Commissioner Murphy said he had decided to resign his membership from the NTPA, arguing "the Association should be strong and should be representative of membership".

"I am incredibly disappointed by the statements made by the association late yesterday in response to my apology to Aboriginal Territorians at the Garma Festival on Saturday," he said.

"I love policing. I know you do too, and I am proud to be your commissioner. I have a vision for the future of NT Police; and in order to achieve that future, we need to be able to understand and acknowledge our history.

"Our shared mission is to serve and protect all Territorians."

Commissioner Murphy's apology on Gumatj land at Gulkula, where he spoke with a white gapaṉ streaked across his brow, was met with applause from the crowd, and cautious commendation from Indigenous groups, who have long-called for systemic change in the force.

Commissioner Murphy also endeavoured to make a separate apology to the Yuendumu people, the community in which Warlpiri-Luritja man Kumanjayi Walker was shot dead by NT Police Officer Zachary Rolfe in 2019.

Rolfe was acquitted of all charges.

"There's a lot of anger towards policing from the community," Commissioner Murphy said.

The ABC reported NT Labor Chief Minister Eva Lawler said the police commissioner "was absolutely right to apologise" and argued that "we do need to move forward, we know there has been racism within the police force in the past".

"We need to have a police force that has a strong, positive relationship with Indigenous people in the Northern Territory," Ms Lawler said.

Territory police have long been shrouded in accusations of institutionalised and systemic racism by Indigenous people in the NT who have argued they've been subject to over-policing, violence, death.

Evidence of this has been dramatically aired at the inquest into Kumanjayi Walker's death, which included a number of racist 'awards' handed out by the elite Territory Response Group (TRG), including for "c**n of the year".

Tensions have only been exacerbated by Commissioner Murphy admitting during the inquest that he knew about the awards for months before they came to light, accepting that he was "effectively gaslighting" people who had made numerous complaints about racism in the NT Police when he told reporters the existence of the certificate and other behaviour outlined by Mr Rolfe was something he had not seen before.

Other allegations include a police sergeant sharing a photo of a topless Aboriginal woman via a WhatsApp group of other officers, but having his demotion halted by the Commissioner; and other 'awards' issued between 2007 and 2015 that ICAC Commissioner Michael Riches considered "so offensive" they weren't in the public interest to circulate.

Kumanjayi Walker's cousin, Samara Fernandez-Brown, told National Indigenous Times earlier this year the existence of racism in the NT Police was something Indigenous community members had long known, and had been making repeated complaints about for years.

"For us, it has been something that has existed forever," Ms Fernandez-Brown said at the time.

"I think when you work within the police force, it's hard for us to believe that anybody within the police force doesn't know that racism exists, because it comes across so obviously to us, particularly Aboriginal and Torres Strait Islander people."