Brittany Higgins was so obsessed with pursuing Bruce Lehrmann over an alleged sexual assault that she refused to help Ten defend his defamation case unless they agreed not to settle, his lawyers say.

In a submission made public on Friday, Lehrmann’s side argues Higgins’ credibility is so poor the court should completely reject her testimony unless it is corroborated by some other source.

“No confidence can be placed in Ms Higgins’ understanding of her obligation to tell the truth under oath or on the most solemn of occasions,” Lehrmann’s submission said.

Higgins had a “preparedness to tell lies” both to the federal government to obtain a “life changing” settlement of almost $2.5 million and to an ACT criminal court during a now-dropped prosecution of Lehrmann, the document said.

The former Liberal media advisor had an “obsession” with securing vindication against her claimed rapist through the courts, including in his defamation case against Network Ten, Lehrmann argued.

Lehrmann is suing Ten and journalist Lisa Wilkinson over a February 2021 report on The Project where Higgins was interviewed about her alleged rape in Parliament House.

She claims Lehrmann sexually assaulted her in the office of their then boss, Senator Linda Reynolds, in March 2019.

In agreeing to help Ten defend the defamation case, Higgins said the network was not to make any offer to Lehrmann to pay him damages, retract the articles, make an apology or pay his legal costs.

“That is an extraordinary position for a witness to take,” Lehrmann’s submission said.

In the document, Lehrmann continued his denials that any sexual activity took place, saying there were “too many other plausible possibilities” about what happened and why Ms Higgins was later found naked in Senator Reynolds’ office.

She could have vomited on her dress and removed it or taken it off because she was afraid of getting sick on it, the submission said.

“The critical point is there are a number of plausible explanations for why Ms Higgins, being affected by alcohol, took off her dress and lay down naked on the minister’s couch.”

Even if the court rejected claims nothing happened, it would still need to find Higgins was unable to give consent in order to show that rape occurred, the submission said.

Lehrmann also sued News Corp and the Australian Broadcasting Corporation over their coverage of Higgins’ allegations.

Both these cases have settled, with the ex-Liberal staffer receiving $445,000 in legal costs under the agreements.

The trial against Ten has concluded and judgment will be delivered at a later date.

Lehrmann was charged in August 2021 over the alleged rape, but his criminal trial in the ACT Supreme Court was derailed by juror misconduct.

Prosecutors did not seek a second trial, citing concerns for Ms Higgins’ mental health.

Lehrmann is also before Queensland courts accused of raping another woman twice in Toowoomba in October 2021.

He has not yet entered a plea, but his lawyers have indicated he denies the charges.

1800 RESPECT (1800 737 732)

National Sexual Abuse and Redress Support Service 1800 211 028

– AAP