Mining magnate Gina Rinehart’s eldest daughter has claimed she was subjected to “constant bullying” to sign a deed and feared if she didn’t her mother would “cut off all financial support”.

“I have always understood my mother to be a very powerful woman, and I have always believed that she would not hesitate to wield that power to get what she wanted,” Bianca Rinehart says in an affidavit released by the Federal Court on Tuesday.

The claims by Ms Rinehart’s two eldest children are part of their most recent legal challenge against their mother.

• Rinehart loses $6 billion as iron ore price plummets 
• How Australia squandered the mining boom

Separate from a Supreme Court case, which centres on Ms Rinehart’s position as trustee of the multi-billion dollar family fund, Bianca Rinehart and John Hancock are claiming in the Federal Court they were pressured into signing a number of deeds without being told of the ramifications.

In the days leading up to signing of one of these deeds – called the Hope Downs Deed – in 2007, Bianca says she was subjected to “constant bullying”.

“I believed that if I did not sign the Hope Downs Deed, my mother was likely to cut off all financial support to me or punish me in some other significant way,” Bianca says in her affidavit.

The pair claim the purpose of this deed was multi-faceted and aimed to effectively prevent and protect their mother and the family’s flagship company Hancock Prospecting (HPPL) from any claims by them as beneficiaries of the multi-billion dollar family trust.

Bianca says she felt compelled to sign the so-called Rose Porteous Deed, which she understood would bring an end to her mother’s protracted dispute with her late father Lang Hancock’s wife.

She said she was having lunch with her then partner and former prime minister John Howard when she got a text on behalf of her mother saying words to effect of “go home … immediately and sign the deed.”

“Although I looked up to my mother, there was a side of her that made me fearful. She could be a bully, she could belittle and she could hold a grudge,” she states.

Meanwhile John Hancock states in his affidavit that he signed the Porteous Settlement Deed in 2003 because his mother said words to the effect of “you cannot hold up a settlement” and that he was still hopeful of winning his “mother’s approval”.

He claims after signing the deed, his mother told him: “You’re not needed anymore”.

Gina Rinehart is pushing for the Federal Court hearings to be dealt with behind closed doors in arbitration proceedings.

– AAP