If former attorney-general Christian Porter loses a senior lawyer in his defamation case it will be a “very big deal,” the Federal Court has been told.

Sue Chrysanthou SC has been using her specialist skills in defamation law over a significant period of time to ensure the federal minister’s trial would be heard this year, her barrister Christopher Withers SC said on Wednesday.

“That might be jeopardised if she can’t act … it is why we are vigorously defending to keep her in the counsel in a case that has the most serious implications for (Christian Porter),” he said.

An application to restrain Ms Chrysanthou from the case comes from Jo Dyer, a good friend of the deceased woman at the centre of rape allegations against Mr Porter – which he denies.

The now-industry, science and technology minister launched defamation action in March against the ABC and journalist Louise Milligan over an article concerning a historical rape allegation against the unnamed cabinet minister.

Ms Dyer is concerned she discussed confidential information with Ms Chrysanthou while she was acting as her lawyer. The extent of their lawyer-client relationship has been disputed in court.

Barrister Sue Chrysanthou.

What was discussed in their November 2020 chambers meeting, and whether it is classified as confidential at the time and remains so, is a key issue for the judge.

Mr Withers submitted that Ms Dyer was a prolific public commentator about the allegations related to her “dear friend,” and cited 15 relevant Twitter comments she made.

Some of her tweets include that the police investigation and Prime Minister’s response to reports had been inadequate, and that she “will not allow this issue to be managed away”.

The inference could be made that Ms Dyer’s discussions with Ms Chrysanthou were made elsewhere in the public domain, Mr Withers said.

Michael Hodge QC, representing Ms Dyer, argued there was no doubt his client’s interaction with Ms Chrysanthou at the time was confidential in nature and considered it a “fishing exercise” to produce every possible communication on the topic, as had been requested.

The defamation case has been frozen until Justice Tom Thawley decides whether there has been a conflict of interest.

A three-day hearing to resolve this has been set down for May 24.

-AAP