It's Bianca v Ginia in latest round

The Hancock family feud descended into claims of bullying and sibling rivalry yesterday as Gina Rinehart's youngest daughter Ginia fought to knock her eldest sister out of contention for control of the multibillion-dollar family trust.

In a day of drama, Bianca Rinehart's lawyers tried to have the civil trial closed to the public and a NSW Supreme Court judge agreed to seal a document containing sensitive allegations against the 37-year-old which were labelled an "improper" attempt to smear her.

Ginia Rinehart's lawyers argued against Bianca's last-minute move to switch places with her brother John Hancock as their candidate for the contentious position of trustee.

Until Tuesday, lawyers for Gina and Ginia Rinehart had been preparing to attack Mr Hancock during this week's long-awaited civil trial over his suitability for the role.

They said yesterday that if Bianca ran in his place, they would need time to investigate her past.

This included her employment history and a series of allegations they had laid out in a confidential affidavit.

One of these, involving an alleged incident in 2004, was attacked by Bianca's lawyer, Christopher Withers, as "improper" and "irrelevant".

Mr Withers asked the judge to close the court while he addressed the claim.

"That was more than nine years ago," he said, after Justice Paul Brereton refused his bid to move the hearing behind closed doors.

"In my respectful submission, it is an entirely improper thing to raise.

"I don't know what the motivation is for it to be raised now."

No details of the allegation were given and Mr Withers asked Justice Brereton if it would be possible to remove the affidavit that outlined the claim from the court's records. Justice Brereton said this was not possible but he agreed to seal the document in an envelope with instructions that it can be opened in future only by an order of the court.

Until now, Bianca had taken a back seat in the family's two-year feud, which has pitted her and brother John against their mother and half-sisters Ginia Rinehart and Hope Welker in a dispute over control of the family trust.

Mr Withers said there was no basis for yesterday's attack on his client, who was "eminently suitable" to be trustee.

"This is nothing more than an attempt to dig up irrelevant material," he said.

"It is just speculation - 'Can we find any reason to oppose Bianca'?"

Mr Withers said statements in support of Bianca had been sworn by Perth investment banker John Poynton and businessman Peter Fitzpatrick.

Ginia's lawyer Richard McHugh said his client had concerns about her sister becoming trustee and said Bianca had battled every member of the family at some point in the past.

"This has been a hard-fought litigation. There is a history of family disputes," he said.

He said Bianca had been in conflict with Ginia and had fought with John, including a stoush between the pair in 2006 over the Hope Downs deed, the secret agreement signed among the family members.

If the court accepted Bianca's nomination, Mr McHugh said, Ginia would want to issue subpoenas and "make inquiries of previous employers", which would require the trial to be adjourned.

He said they would need to investigate the circumstances under which Bianca left her role as a director of Hancock Prospecting soon after she helped launch the legal action against her mother.

He would also need to examine whether she tried to pressure her younger sister Hope not to withdraw from the legal action this year. They would also need to know whether there had been any "funding agreements" made.

"The principal problem is that Bianca Rinehart is one of four siblings who in the last few years have had several disputes," Mr McHugh said.

Mr Withers said the attacks were baseless. He said if Hope had had an issue with Bianca, as Mr McHugh had implied, she would have objected to her sister being accepted as a nominee, which she had not done.

Justice Brereton said resolving the trustee issue would not be easy or straightforward and he would prefer to accept Bianca's bid and have as many options before him as he could.

But he said allowing her to nominate would be an injustice to Mrs Rinehart and her daughter's lawyers who had not had time to prepare arguments addressing the Bianca scenario.

Last week, Mrs Rinehart agreed to do what her children had demanded and step down as head of the family trust. On Monday, just hours before the civil trial was due to start, she proposed a new structure for the management of the trust, which they refused.

Unless John Hancock renews his bid to be trustee when the court resumes today, the only option will be a proposal by Ginia for an independent trustee and a separate one, by Mr Hancock, to appoint Adelaide accountant Bruce Carter.