Guidelines dictate that both parents must provide consent for their child to attend and for the information to be shared with the courts, but in the majority of cases locally, at least one parent objects.

Laurel House chief executive officer Justine Brooks said the Federal Courts lacked investigative powers and were relying on state-based service providers, who in turn faced their own restrictions.

She said the current system is allowing the person who may be causing the child's trauma to prevent them from accessing trauma support services.

"This is a flawed system when some service providers, such as Laurel House, are restricted from participating or even gathering that information when one parent does not provide or withdraws consent for the child to see us," she said.

"Unfortunately, this is a common event which can be really traumatic for the other parent who is seeking support for their child.

"Obviously a parent who may be perpetrating would be unlikely to agree for that child to have counselling with us because of what they might disclose, but that is not the only reason one parent may decline permission."

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With a third review of the family law system in three years approaching, Laurel House is urging changes to allow them to work with a child without the consent of both parents "if there is a strong suspicion that something untoward is occurring".

"This suspicion might occur through early sexualised behaviours or even the child disclosing to another party," Mr Brooks said.

At the moment, Laurel House can only seek advice from, or notify, the Strong Families Safe Kids referral line that they have concerns about the child.

The organisation does not act in an investigative capacity, but must comply with mandatory reporting requirements if a child mentions sexual abuse.

The 2017 federal parliamentary inquiry into "a better family law system to protect those affected by family violence" made several recommendations with the rights and welfare of children at its core.

These included an examination of ways in which children's perspectives could be better heard in court, and an extension of a pilot program that offers referral pathways to specialist support services for families with "additional challenges".

The Australian Law Reform Council review of family law, released earlier this year, recommended establishing a Children and Young People's Advisory Board to provide advice on children's experiences with the system.

The announcement of a third review - to be co-chaired by One Nation senator Pauline Hanson - drew criticism from legal practitioners and support services, who believed the previous inquiries included all relevant information.

Attorney-General Christian Porter was contacted for comment.