Noel Hutley SC detailed the spat in the late 1980s as he made Hancock Prospecting's defence case against the company of Lang Hancock's former business partner, Wright Prospecting.
"After the death of his first wife and the commencement of his involvement with Rose Porteous and later marriage to her, unfortunate difficulties arose between (Mr Hancock) and his daughter Gina Rinehart," he told a complex trial over mining assets and royalties in Western Australia's northwest on Thursday.
"He started at the behest of Rose Porteous spending vast sums of money on mansions and the like."
Mr Hutley said the spending spree caused Mrs Rinehart, who had significant interests and positions in the company and its subsidiaries, to raise questions about her father's conduct.
"Lang Hancock's response to that ... was to remove Mrs Rinehart from the directorships of Hancock Prospecting," he said.
He also removed Mrs Rinehart from other positions within the company structure and diverted lucrative opportunities "to keep her in the dark".
The revelation was made as Mr Hutley told Justice Jennifer Smith about a series of memorandums, meetings and a 2005 agreement with Rio Tinto that he said showed Wright Prospecting knew it did not hold a share in the multi-billion-dollar Hope Downs assets or rights to royalties, which the Supreme Court trial is based upon.
Wright Prospecting has demanded a share of Hope Downs tenements and royalties amid a claim it never relinquished the assets held by the Hanwright partnership and Hancock Prospecting has breached a series of partnership agreements
Mr Hutley said Mr Hancock attempted to leave the income and tenements from Hope Downs and East Angeles (now also known as Hope Downs) to Ms Porteous in what he described as a "textbook case of breach of fiduciary duty".
"Shortly before his death he realised the errors of his way and started to undo his wrongdoings," he said.
He said Mr Hancock showed "no regard" for Wright Prospecting's interests, which was contrary to the company's claim that he was acting for the Hanwright partnership.
"He diverted these tenements without ever disclosing to Mrs Gina Rinehart or any other shareholder of Hancock Prospecting the full details of what he was doing," Mr Hutley said.
"Sadly and wrongly Lang Hancock deliberately went about to deprive Mrs Rinehart from the ability to obtain information by removing her from all positions."
Mr Hutley said it resulted in all the tenements being held on trust for Hancock Prospecting and not the partnership.
"Lang never acted in (Wright Prospecting's) interest and was solely focused on his own self-interest," he said.
He said it also likely meant that Mrs Rinehart's children's competing claim for a stake in the lucrative Hope Downs mining project was irrelevant
"My client takes no joy to revisit the events of the 1980s and to address the court on its founder Lang Hancock's breaches."
He said it was a short part of a much longer career devoted to developing the Pilbara region's iron ore resources.
"It was a period in which he succumbed principally to the pressures of Rose Porteous and her desire for a luxurious lifestyle," he said.
Mr Hancock died in 1992, triggering a long legal battle over the family fortune between his daughter and his Philippines-born widow whom he'd hired to be his housekeeper before marrying in 1985.
