A "catastrophic" failure to protect people in Victorian disability care from assault and sexual predators is being investigated after families of victims say they were ignored.
Anne Mallia told the ABC's Four Corners program her son was groomed by a predator while he was in care with Autism Plus in Victoria, but her reports were ignored.
Maria Thomas also told the program her son was being targeted by the same man, but when Autism Plus urgently asked the Department of Health and Human Services to move the man, the request was rejected.
"(My son) was sexually assaulted in the shower while he's having a shower," Ms Thomas told the ABC.
Beverley Swann said her brother had been assaulted in a Lifestyle Solutions home and it was covered up.
Jean Hislop said her son was sexually assaulted by a staff member in a home run by the Victorian DHHS.
Autism Plus general manager of operations Edward Boghikian said he welcomed the government investigation into the claims, but was legally prevented from commenting on the case.
"We're bound by confidentiality and we hold the privacy of our clients in such regard that even in the face of public scrutiny we still will not breach it," Mr Boghikian told AAP on Tuesday.
When asked if he was confident the department would properly handle an issue if he contacted them, Mr Boghikian said: "I can't answer that question, it was a good question, but I can't answer that."
Victorian Human Services Minister Martin Foley said the department's interactions with Autism Plus and Lifestyle Solutions were being reviewed.
"It is also evident that my department needs to do more to ensure people with a disability are not continued to be let down in any way," Mr Foley said in a statement.
Premier Daniel Andrews said the government would learn from the "tragedy" and the pain caused to families.
"When something like this happens, you must acknowledge that it is a catastrophic failure," he told reporters.
Lifestyle Solutions chief executive Andrew Hyland said he was "deeply saddened" by the stories.
"Where shortcomings were identified, the findings have informed improvements in our policies and procedures," he said in a statement.
The Australian Federation of Disability Organisations said a 2015 Senate inquiry recommended a Royal Commission into abuse in disability care.
"We need providers to be held accountable for what happens on their watch," chief executive Ross Joyce said.