A growing number of children in youth custody claim they have been brutalised by police, including one recent case where a boy was hospitalised with serious injuries and another in which a young person was allegedly bitten dozens of times by a Victoria Police dog.

Authorities have confirmed a spike in the number of young offenders who have raised allegations of excessive force over the past few months – including a disproportionate number of complaints from Indigenous youths.

Andrew Jackomos, Victoria's Commissioner for Aboriginal children and young people, has demanded a joint review with Victoria Police.

Aboriginal Children's Commissioner Andrew Jackomos said that in the past week alone he had been made aware of at least three cases involving Koori children who were allegedly mistreated before they were transferred to a youth detention centre.

One of those cases was so serious that the young victim was reportedly taken to the Royal Children's Hospital with suspected spinal injuries, head trauma and a fractured limb, while in another incident, a young person ended up with "about 40 bite marks" from a police dog, he said.