THE son of billionaire mining magnate Gina Rinehart has lashed out at Agriculture Minister Barnaby Joyce's "dangerous" intervention in the court battle over a $5-billion trust, and questioned whether the potential Nationals Leader is fit to serve as a cabinet minister.
Mr Joyce did not respond to repeated requests for comment on his highly personal email to one of Mrs Rinehart's children, urging her to drop her legal action.
The Opposition has called for Prime Minister Tony Abbott to haul in his minister and demand an explanation for the "extraordinary" intervention.
John Hancock, the estranged son of Australia's richest person, last week won an epic legal battle over control of the family trust, with his sister and ally Bianca Rinehart appointed trustee.
NSW Supreme Court Justice Paul Brereton appointed Bianca, 38, trustee of the Hope Margaret Hancock Trust, set up by her grandfather Lang Hancock. In handing down his judgment, Justice Brereton said he had "never seen such pressure exerted, so persistently, on a litigant", as in this case.
Some measures "closely approached intimidation", Justice Brereton said.
The judgment cited two letters sent by Mr Joyce and the now retired Liberal MP Alby Schultz to Mrs Rinehart's other daughter, Hope Welker.
In the email Mr Joyce wrote: "Australia needs strong families and Hope we need, really need, yours to be strong".
"Your family are good people, if they were not I would not care as much about you and your mum," the email continued.
"You are a family Australia needs. All good families have their problems but before it gets really out of hand, I would try to get it back in house and out of public view."
The note was sent from Mr Joyce's parliamentary email address and describes how his family had been racked with conflict over his decision to marry his wife. "I was the one who had been flicked because I had the temerity to choose my own wife away from the New England stud book," he said.
He suggested lawyers would not have her interests at heart. "Lawyers get you to say nasty things. They stir you up then turn the account clock on and watch the money flow," he said.
Mr Joyce also criticised the media. "Hope, I live in the public gaze, a lot of my life I do not enjoy because every move is on television and in the press. But Australia asks different things of different people."
He went on: "Hope, once the public interest starts looking into your private life then every mobile phone is one step away from you being on YouTube. You can not control it."
Mr Hancock said on Friday that Mr Joyce had questions to answer and raised doubt over whether he should continue serving as a minister.
"Is this the type of person who should be sitting in federal cabinet?" Mr Hancock asked Fairfax Media. Mr Hancock said that, by using his government email address to send an email urging Mrs Welker to drop the court action, Mr Joyce had involved the Abbott government in the dispute.
"This character sits three chairs down from the Prime Minister. To have someone so easily manipulated, or alternatively so naive, is dangerous in such a position," he said. "By doing so he endorsed the conduct of Gina Rinehart and involved the Australian government."