People charged with rape or sexual violence were referred by the Department of Corrections for treatment.
But Harmful Sexual Behaviour Sector chief executive Lesley Ayland said most victims were abused by someone they knew, and many of them did not want to press charges because they were reluctant to go through the court system.
But most providers were funded only for referrals from Corrections, or for cases involving young people.
Ms Ayland said her organisation's contracts with government agencies specified that it could not see any perpetrator who had a victim older than 17.
"That means we have no services anywhere in this country for adults who have sexually assaulted adults ... and have not been charged."
Providers said that if services were available, abusers often came forward voluntarily.
Children who committed sexual abuse at schools also fell through a loophole. Unless they were a threat to their siblings or parents, Child Youth and Family did not refer them or their victims for treatment.
Equal Opportunities Commissioner Jackie Blue told the committee that gaps in the current system meant that some victims were not able to recover from the trauma of rape or sexual abuse.
"Sexual abuse can cause pelvic floor muscle dysfunction, incontinence and other problems ... A person with similar injuries from a jetski was able to get physiotherapy access for services," she said. "But the person who had sexual abuse [which] resulted in those injuries was unable to. It just seems bizarre."