Rinehart’s estranged children, John Hancock and Bianca Rinehart, have launched fresh legal action challenging the ownership of Hancock Prospecting.

“My mother has transformed Hancock Prospecting to become Australia’s largest and most successful private company,” Ginia Rinehart said in a statement issued through a spokesman.

“She did it despite many difficulties, through very hard work and dedication.

“This should be dealt with in private arbitration, as everyone had previously agreed to, and not by breaching deeds, and by yet another court case.”

Lawyers for Hancock Prospecting have argued for the details of the case to remain private and there is a temporary suppression order in place.

According to AAP, Hancock Prospecting QC John Sheahan told a Federal Court hearing in Sydney on Tuesday that there was “real risk of commercial harm” if details of the case were made public.

A spokesman for Hancock Prospecting said the company was focused on the development of the $A10 billion Roy Hill mine, which continues ahead of schedule with more than 7200 people employed.

“It is a fantastic achievement to be currently ahead of schedule for a major resource project in Australia, with such an aggressive schedule,” he said.

“In addition many thousands more jobs Australia-wide are supported by Roy Hill's works.

“It is a project for Australia of international significance being undertaken in increasingly difficult times for mining in this country.

“This action will be defended, and in the meantime work on the project continues despite distractions.”

With first ore on ship targeted by September next year, Roy Hill will ramp up to 55 million tonnes per annum of iron ore.

Earlier this week, Hancock Prospecting posted a full-year profit of $88 million from revenue of more than $2.6 billion.