The senate committee report published on Monday found conditions on Nauru were not "appropriate or safe" for detainees.
It said allegations of rape and abuse should be investigated and access given to journalists and rights workers.
All people who try to get to Australia by boat as refugees are detained in off-shore centres like Nauru.
Immigration Minister Peter Dutton said the report had been "a witch hunt".
The committee report was based on six months of investigations and public hearings.
(BBC News)