The children of Australian mining magnate Gina Rinehart are on a "Kamikaze mission" that could destroy her iron ore company and endanger a joint venture with Rio Tinto, a court was told today.

It is the latest twist in one of the most extraordinary family business wrangles, playing out in a series of complex legal disputes in the New South Wales Supreme Court.

A lawyer for the billionaire's Hancock Prospecting told the court that changes to the family trust could jeorpadize the agreement with mining giant Rio to develop a mine at Hope Downs in Western Australia.

"The damage would be enormous" and "irreparable,"David Studdy told New South Wales Supreme Court, according to Bloomberg wire agency.


John Hancock and Bianca Rinehart allege their mother acted "deceitfully" and with "gross dishonesty" in her dealings with the family's $5 billion trust fund, set up in 1988 by her father, Lang Hancock, to benefit her children.

They allege that in 2006, Ms Rinehart changed the constitution of the family company, Hancock Prospecting Pty Limited, in such a way as to prevent her being removed as trustee.

And they are moving to replace their mother as trust manager with a non-family member.
But Mr Studdy was quoted as saying appointing an independent trust would put a quarter of Hancock Prospecting's shares outside of the family's direct control, breaching the accord that requires it to wholly own and control the company.

Last week, Ms Rinehart's barrister Noel Hutley dismissed claims that the mining magnate had tweaked the deed in her favour in a "cunning plan, worthy of Baldrick", in a sarcastic reference to British comedy series Blackadder.