Gina Rinehart has lost a bid to have her children's multibillion-dollar family trust claim dealt with through confidential mediation and not in open court.
Last September, the three eldest children of Australia's richest person launched a NSW Supreme Court action against their mother.
They want to oust her as trustee of the family trust, claiming she had acted with "gross dishonesty" and "deceitfully" in her dealings with the trust.
But Ms Rinehart tried to stay the proceedings, arguing that she and her children had entered into a deed requiring all family disputes to be settled through confidential mediation and, if that failed, confidential arbitration.
Last October, Justice Paul Brereton rejected her application, finding the claim was not a "dispute under this deed".
On Friday, the NSW Court of Appeal dismissed Ms Rinehart's challenge to the decision.
The Appeal Court agreed the claims made by the children were not disputes "under this deed"."The phrase 'under this deed' has consistently been given a narrower construction than phrases such as 'arising out of the deed' or 'in connection with the deed'," the court said.