The four-year-old claimed he was molested by his father - and an independent review has criticised Families SA's role in the case, The Advertiser reported.

The Family's Court's custody ruling came despite an internationally renowned child abuse expert giving evidence that the behaviour of the boy made it clear it was highly likely he had been seriously abused.
The review findings were made by John Leatherland, of the Victorian Child Death and Serious Injury Review Committee, after being commissioned by then-Families Minister Jennifer Rankine following the mother's repeated complaints.

Mr Leatherland says Families SA failed to comprehensively investigate the context and content of CCTV footage which showed the boy and his younger brother engaging in highly sexualised conduct.

The boy later named their father as their abuser during a police interview.

While making no ruling on whether the children were abused, he said "insufficient weighting" was given to the footage, later used in evidence by the mother but dismissed as normal conduct by the trial judge.

The expert said numerous eminent people had seen the footage - including psychiatrists and federal MPs, all of whom said they were appalled it was accepted as normal behaviour.

"Even if daddy had shown them so much hardcore porn that it resulted in serious emotional disturbance and re-enactment, that would still constitute child abuse," the expert said.

The mother, who has visitation rights, said she would not have reported the alleged abuse if it meant she would lose custody of both children.

"I just wish I had not reported it; now the State Government or the Family Court won't give them back," she said.

"I'll guarantee never to report the (alleged) abuse again so at least I get to see them and take care of them for half the time," she said.

"Families SA would rather leave my kids at risk than admit they made a mistake."

The mother has launched an appeal against the Family Court's decision.