The ABC has revealed it will rely on qualified privilege and truth in its defence against a defamation claim brought by former Attorney-General Christian Porter.

Mr Porter is suing the public broadcaster and journalist Louise Milligan in the Federal Court for a story about an anonymous letter being sent to the Prime Minister, attached to a 31-page dossier detailing a historical rape allegation from 1988 levelled against a serving Cabinet minister.

The article, published in February, did not name the Attorney-General as the subject of the complaint, but Mr Porter's legal team claim he was easily identifiable.

He has strenuously denied the allegation and his lawyers argue he has been the subject of "trial by media".

Nearly a week after the ABC article was published, Mr Porter publicly identified himself.

Today the Federal Court heard the ABC's defence had not been made public, because Mr Porter wants part of it struck out under the court's evidence rules relating to frivolous, scandalous, vexatious or prejudicial material.

The ABC's lawyer Renee Enbom told the court the three schedules Mr Porter wanted cut out contained a substantial part of the ABC's case.

Ms Enbom said it was unfair that Mr Porter's claim was in the public domain when the ABC's was not.

Mr Porter's lawyer Sue Crysanthou told the court her client was not trying to keep the ABC's defence secret.

"Noone is seeking to keep the bulk of the defence from the public, only the schedules," she said.

The court has agreed to release a redacted version of the ABC's defence and a 13-page reply by Mr Porter's lawyers, pending a hearing at the end of May to consider the contested issues.

The ABC says it would prefer the matters to be in the public domain.

Also during today's hearing, some of the key differences between the parties emerged.

Ms Crysanthou told the court there was a need to hold the substantial hearing earlier rather than later.

She suggested three weeks be set aside for the hearing and also offered a way to shorten the trial by separating some issues.

But Ms Enbom told the court the ABC had a complex case to compile and predicted a timeframe of about six weeks.

"There is a qualified privilege defence, there's also a substantial truth defence to many of the alleged imputations," Ms Enbom said.

She told the Federal Court the ABC planned to call 15 witnesses.

The court is considering a hearing to start in October.

Last year, prior to the article being published, the woman who made the claims took her own life.