Christian Porter’s barrister should not have had to step down from acting for him in a defamation lawsuit against the ABC because of ill will felt by the friend of his accuser, a court has been told.

The former attorney-general is appealing the disqualification of barrister Sue Chrysanthou SC and about $500,000 in potential costs after losing a legal battle against a friend of the woman who alleged she was raped by Mr Porter in 1988.

That friend, Jo Dyer, consulted with Ms Chrysanthou about a potential defamation claim against The Australian in 2020 and provided confidential information to the barrister that was potentially relevant to Mr Porter’s lawsuit against the ABC, Justice Tom Thawley found in May last year.

On Wednesday, Bret Walker SC argued on behalf of Mr Porter that there was no rule letting a barrister refuse a brief because it was “embarrassing” or because of past professional relationships, saying Ms Dyer had obviously disapproved of the former attorney-general.

“Mr Porter is obviously somebody to whom [Ms Dyer] has exhibited a high level of disapproval, wishes him ill to put it bluntly,” Mr Walker told the Full Court of the Federal Court.

The appeal focuses on the claimed confidentiality of the information given to Ms Chrysanthou and whether or not it was relevant or could be misused in the defamation case against the ABC.

Ms Dyer’s barrister Michael Hodge QC argued that Mr Porter had misunderstood Justice Thawley’s decision, saying that Ms Chrysanthou could have subconsciously used confidential details given to her by Ms Dyer in the ABC’s defamation case.

“It’s not about the idea that there’s a duty of loyalty owed … It’s about the proposition that a lawyer owes a duty of confidentiality to the client,” Mr Hodge told the court.

Also on Wednesday, there were questions about the level of secrecy regarding evidence, with Justice Michael Lee noting the “extremely sweeping confidentiality orders” that had already been made in the case.

Mr Walker agreed, pointing out that the matter was not one of national security.

Mr Porter has emphatically denied the allegation brought by the woman, known only as AB, saying that sex between them never occurred.

The woman took her own life almost two years ago and Mr Porter settled his defamation action with the ABC in May last year.

Mr Porter resigned as the federal minister for industry in September after failing to explain who was behind an anonymous “blind trust” donation to pay for his defamation case. He will quit politics at next month’s election.

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– AAP