NSW State Parliament Minister for Family and Community Services, Pru Goward.

Child brides ''quite common'': Minister for Family and Community Services, Pru Goward. Photo: Wolter Peeters

NSW Police had never arrested anyone in relation to child brides until last week.

So it was news to child abuse detectives that underage marriages were a ''significant'' problem across Sydney.

In the past week police arrested three men accused of their involvement in the marriage of a 12-year-old girl during an illegal Islamic ceremony.

A 26-year-old Lebanese student who married the girl and her father will remain in custody until their next court appearance.

Upon hearing of the child-bride case, Community Services Minister Pru Goward told 2GB radio that forced marriages of young girls may be ''quite common''.

Ms Goward said anecdotal evidence suggested forced marriages between children and adults was an ongoing issue among Sydney communities.

''I understand there are actually a significant number of unlawful, unregistered marriages to underaged girls in NSW, particularly in western Sydney, south-west Sydney and the Blue Mountains,'' she said.

Child abuse detectives said they had not received any information about underage marriage being a widespread problem.

''We've received no previous reports of this type of incident or this type of crime [underage marriage in NSW],'' Detective Inspector Betell, of the Child Abuse Squad, said.

He said his squad had once received information some years ago about the possibility of a young girl who was sent to Pakistan for a forced marriage.

The tip-off came from an anonymous source which officers were not able to act upon. Apart from that he said a report was made in 2010 about an incident dating back to 2003 but no charges were laid.

''Other than that - of young brides forced into marriage in NSW - we have no previous reports,'' Detective Inspector Betell said.

''It is difficult for the child abuse squad to investigate these types of crimes when there is no knowledge of it or reports of it.''

When Ms Goward was asked why police were not aware of child marriage being a widespread problem, a spokesman said: ''This would be a matter for the police.''

Ms Goward said she had heard only anecdotal reports of specific cases, often discovered only after a girl had turned 18.

The Minister said she was aware census data suggested that a large number of girls were possibly involved in illegal relationships but warned there were varying circumstances.

''There can be many different circumstances in these situations, from true child abuse, to a 17-year-old girl running away from a dysfunctional family to stay with a boyfriend or another family,'' Ms Goward said.

''Every situation is no doubt unique, but I don't think any reasonable person in the community would condone a relationship such as we have seen reported in recent days."

Detective Inspector Betell said to the best of police knowledge, the arrests of the three men in relation to an underage marriage was a first in NSW.