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Lack of action on deaths in custody a stain: NSW Greens

Stymied progress on Indigenous deaths in custody has left a "stain" on the relationship between First Nations people and the NSW government, the Greens say.

The minor party has committed to justice reforms during the next term of NSW parliament and raised the alarm over One Nation's campaign to expand its influence in the upper house, calling the party "toxic" and "divisive".

"It's time that the incoming government actually takes action and listens to those voices," Greens upper house candidate Lynda-June Coe told reporters on Thursday.

"Families are continuously not accorded any form of justice, and it continues to be a stain between the relationship of Indigenous peoples and the government."

The party also wants to reform investigations into deaths in custody so they are no longer carried out internally by the NSW Police Force.

"For over 200 years in this country, First Nations people have been subjugated to a regime of elimination, based on dispossession, and a continuing need to contain us as a colonised people," Ms Coe said.

It comes after NSW Labor committed to establishing an Indigenous-led treaty process if it forms government after the March 25 election.

Greens MP Jenny Leong has welcomed the move but says Labor needs to also commit to a truth-telling process, to recognise the mistakes of former governments.

The Greens also propose creating a plan for independent police and prison oversight with the power to refer officers for prosecution, and increasing funding to legal services.

It also wants to raise the age of criminal responsibility to 14, and the minimum age for custodial sentences to 16.

Ms Leong also raised concerns over One Nation's push to have Bankstown MP Tania Mihailuk, who defected from the Labor Party last year, elected into the upper house.

The makeup of the upper house could come down to a contest between Ms Coe and Ms Mihailuk.

"Until we see a Labor and Liberal government ruling out their willingness to work with One Nation and (leader) Mark Latham, he will still hold some power in the parliament," Ms Leong said.

Mr Latham says One Nation has focused its campaign on positive policies like easing the cost of living and boosting education outcomes.

"We don't regard Jenny Leong as relevant to our election policies or campaign," he told AAP.