In an affidavit as part of a $4 million legal claim on Mr Hawke's estate, Rosslyn Dillon alleges she was sexually assaulted by the late Victorian Labor MLC Bill Landeryou.

Ms Dillon, Mr Hawke's youngest daughter with his first wife Hazel, claims when she told the aspiring prime minister of the allegations in the 1980s, he told her, "You can't go to the police," The New Daily reported on the weekend.

"You can't. I can't have any controversies right now. I am sorry but I am challenging for the leadership of the Labor Party," she says in the affadavit lodged last week in the NSW Supreme Court.

Mr Hawke led Labor to victory in the federal election in March 1983, a month after winning the party's leadership.

Mr Hawke's eldest daughter Sue Pieters-Hawke said she hoped the allegations won't change the way Australians thought about her father, who died in May.

Speaking on Monday at an event honouring him on what would have been his 90th birthday, Ms Pieters-Hawke said it would be "foolish if they did".

"I've made it very clear ... that I love and respect my sister, I disagree with her on (the process of challenging the will) and apart from that I will be making no public comment," she told reporters in Sydney.

Ms Dillon's allegations are the "subject of an affidavit which may or may not be tested in court and I'm not going to comment on any of that," she said.

The family are "pretty well as far as I know," following the reports, Ms Pieters-Hawke said.

Mr Hawke's stepson Louis Pratt said the claims are "news to me" and that the family are "all surprised, obviously."

"Because I know that Bob loved Rosslyn very much and I know what his character is, so it's surprising," he said.

Ms Dillon, who is reportedly living on welfare payments, is claiming $4 million from her father's will rather than the $750,000 given to each of his three children and Mr Pratt, the son of his widow Blanche D'Alpuget.

The New Daily reports the couple's family home in Sydney sold for $14.5 million before his death.

In the affidavit, Ms Dillon says she was "shocked and hurt" her father asked her to cover up the alleged rapes.

"I thought to myself I could not make any bigger sacrifice to the (my father's) political career if I had tried.

"He asked me to let the matter go for him and I did so for him.

"I am still haunted by the sexual assaults. I feel that I may have had a chance to get over these rapes if I was able to report the incidents to police."

Australian Associated Press