A key witness and friend of the woman at the centre of rape allegations against Christian Porter has threatened the former attorney-general with legal action.

Jo Dyer issued a defamation concerns notice against Mr Porter over comments he made about her outside court.

Ms Dyer alleges Mr Porter, who has consistently and strenuously denied the rape allegations, defamed her in a statement on May 12 and on May 31.

“He should be on notice that if I launch legal proceedings, I tend to see them through to their conclusion,” Ms Dyer said in a statement released by her lawyers on Tuesday.

The May 31 comments relate to a lengthy interview Mr Porter gave on Monday after revealing he had discontinued his defamation case against the ABC and journalist Louise Milligan over its reporting of the rape accusations.

A concerns notice is a letter sent to the person alleged to have made the defamatory statement and seeking a remedy (such as an apology).

Mr Porter took action over a February 26 article about a now-deceased woman’s claim he had raped her decades earlier.

Tweet from @instanterudite

There were also other developments in the case on Tuesday, with a judge raising a significant issue with the agreement struck between Mr Porter and the broadcaster. It seeks the destruction of some documents held by the Federal Court.

As part of the settlement, both parties were to ask the Federal Court for an order that sections of the ABC’s defence be permanently removed from the court file.

The sections are under an interim suppression order after Mr Porter raised an objection and applied to have the defence struck out.

But Justice Jayne Jagot said she would have to be convinced why the court should remove files held by the court.

“You’ve filed orders in a court, it doesn’t then become a matter for you about what is to be disclosed or not disclosed,” she told the parties on Tuesday.

“I want to keep the costs as low as possible but this is an unavoidable issue if you want to press [the order].”

The ABC took a neutral position on the matter, while intervening parties Nine and News Corporation continued to push for the release of the documents.

“Our position is it is a consent order between the parties,” a lawyer for Mr Porter said.

“That’s not the point,” the judge responded.

There must be a reason to remove something from a court file, and it wouldn’t be done purely because parties wanted it, Justice Jagot said.

“There is a fundamental issue about the integrity of the court file and why a court would allow the removal of a document from a court file,” she said.

A hearing on the issue will be held in coming weeks.

Given that, the court has not signed off on the settlement agreed between Mr Porter and the ABC.

Should the settlement fall apart, the case could be revived and progress to trial.

As part of the settlement announced on Monday, the ABC has added an editor’s note to the February 26 article acknowledging Mr Porter is the “unnamed cabinet minister”.

The note says the ABC “did not intend to suggest that Mr Porter had committed the criminal offences alleged” and that it didn’t contend the accusations could be substantiated to a civil standard.

-with AAP