The case of a father who allowed his 12-year-old daughter to marry ''for love'' may be one of at least 250 similar incidents across the nation in the past two years, a legal expert has warned.
National Children's and Youth Law Centre director Matthew Keely said a recent study revealed that there were 80 such cases in one capital city alone, meaning the actual figure was certain to be even higher.
''We need more research so that the issue is better understood,'' Mr Keely said.
''It is an issue which is widely acknowledged as under-reported … the exact figure is unknown.'' Mr Keely said the report into child marriage was the first of its kind to address prevalence, and more needed to be done by the government agencies to understand how widespread the problem was.
His call for more awareness came after the arrest of a 61-year-old man who allegedly allowed his 12-year-old daughter to be ''married'' in his Hunter Valley home this year.
Police allege he allowed the child bride to be ''joined in an illegal union'' and start a sexual relationship with a 26-year-old man visiting from Lebanon.
Despite the girl's father arguing she was a ''strong-willed woman'' who was ''in love'', magistrate Caleb Franklin found he had total disregard for Australian law and would not permit his release.
Mr Franklin told Raymond Terrace Local Court the facts indicated the defendant believed he had done nothing wrong.
''Even if the allegations against him are proved he believes there is nothing wrong with the behaviour alleged,'' he said.
''The defendant has a disregard for the laws of this state.''
A Legal Aid solicitor told the court her client denied many of the allegations.
''He certainly denies facilitating or setting up any arrangement. She [the victim] is a very, very mature and strong-willed young woman. He says they are in love and it is a very strong love,'' the solicitor said.
The court heard the accused was worried about his children, one of whom was in tears the last time he saw her. It will be alleged that after hosting an illegal Islamic ceremony in his home, the girl's father then allowed her to move to south-western Sydney with a man who was visiting Australia on a student visa.
The father's arrest came the day after a Muslim cleric was charged with conducting the illegal marriage. Imam Muhammad Riaz Tasawar, from Pakistan, will face court in April.
His alleged actions were condemned on Wednesday by the Australian National Imams council.
Grand Mufti of Australia Ibrahim Salem expressed his shock and said ''that such behaviour is to be rejected and condemned from a legal and ethical prospective''.
The 26-year-old man who ''married'' the girl remains in custody, charged with 25 counts of sexual intercourse with a child.
It is understood the victim was born in Australia and started wearing the hijab to school when her father converted to Islam.
She now identifies herself as Muslim and once wrote a blog about her experiences of wearing hijab to school.
Police were made aware of the underage marriage when the 26-year-old university student applied at Centrelink to become the child's guardian.