Reams of internal Comcare and Department of Immigration and Border Protection documents - released to the Australian Lawyers' Alliance (ALA) under freedom of information laws - paint a damning picture of what the ALA calls under-reporting of safety breaches "at best", and concealment at worst.

They show that of 1092 injuries,and assaults reported to Comcare by the Department of Immigration and Border Protection and its contractors over two years, almost 850 went uninvestigated.

Comcare is required to investigate so-called "notifiable incidents" and to put in place measures to improve safety based on those investigations. But the ALA claims Comcare takes a narrow view of the sort of incidents it should investigate in detention centres.

A Comcare spokesman said the Department of Immigration and Border Protection was only required to notify the authority about "deaths, serious injury or dangerous incidents", and that sexual assault may not be seen as serious enough to warrant a Comcare investigation.

"Incidents of self-harm and sexual assault, for example, may not satisfy the definition of a notifiable incident," the spokesman said.