Papua New Guinea officials have been unavailable for comment on claims that police officers routinely beat children in custody.
The New York-based group Human Rights Watch says officers of the Royal Papua New Guinea Constabulary use guns, bars, batons, hoses and chairs to beat children.
The report also alleges PNG police often rape women, men, girls and boys, in custody.
The group's children's rights researcher Zama Coursen-Neff, says police violence has become institutionalised.
"It has become part of the institutional culture of policing and that's why it's so important to address the overall style of policing, which involves a great deal of violence, now for children in Papua New Guinea."
Ms Coursen-Neff says police reforms don't go far enough... and the scaled-back Australian police advisory programme means the challenge is even harder.