CANBERRA: As much as 90 per cent of child sex abuse is the result of incest, with the perpetrators often being the victim's adolescent brother, research suggests.

"It is still not widely appreciated that much of that offending is actually perpetrated by adolescents and, in particular, brothers of victims," a report by the Australian Institute of Criminology (AIC) said.

The AIC researchers said that estimating the extent of the abuse was difficult as there had been comparatively little focus on the issue of adolescent sibling incest.

"However, estimates of the proportion of intrafamilial abuse which occurs between people from the same generation range from 40 to 90 per cent," it said.

"It is clear that sexual abuse of children by other children or adolescents constitutes a significant proportion of sexual offending against children."

The report said around half of intrafamilial adolescent sex offenders were themselves victims of sex abuse.

As well, families where sibling incest occurred were frequently dysfunctional, with evidence of drug use, sexual abuse by an adult care giver, physical and emotional abuse and neglect.

"Almost three in every four offenders had either no contact or minimal contact with at least one biological parent," it said.

The report said sexual abuse of a child victimised and potentially damaged the child. It recommended a need to understand adolescent sex offending as a health issue, rather than a moral one, for the best possible chance of ending the abuse.