Raising the age of criminality will be the prime topic when a leader of Victoria's peak Indigenous assembly speaks at the state's Yoorrook Justice Commission.
First Peoples' Assembly co-chair Aunty Geraldine Atkinson will give evidence at the truth-telling inquiry on Tuesday, after last week calling on the government to raise the age of criminal responsibility from 10 years to at least 14.
In an open letter published on Thursday, Aunty Geraldine urged the Victorian government to change the system because too many Indigenous children were ending up in custody.
"We need reform, yesterday," she said in the letter.
"I urge you to listen to First Peoples. Listen to your own conscience, which surely must tell you that children do not belong in prisons. And act now."
Premier Daniel Andrews said his government wanted a change to the age of criminality but it would only come through a national approach.
Aunty Geraldine, a Bangerang and Wiradjuri elder, is also expected to discuss the child protection system in her evidence to the commission.
The truth-telling inquiry is the first of its kind in Australia, with its public hearings coming as Victoria embarks on a process towards a treaty or treaties with Indigenous peoples.
During weeks of evidence, the commission has heard directly from stolen generation survivors about their experiences.
Aboriginal leaders have also shared stories of racism and discrimination within the child protection system, where Indigenous children make up 20 per cent of those in care.
They have called for a standalone Aboriginal child protection system and greater funding and resources for Aboriginal-controlled services.