Mr Roberts-Smith, in a long-running defamation action, is suing The Age, The Sydney Morning Herald and The Canberra Times over media reports from 2018 related to his deployments in Afghanistan that he says paint him as a war criminal.

In separate proceedings, Mr Roberts-Smith took action last year against his ex-wife Emma Roberts - slated to testify for the media outlets in the civil trial - to examine her over compliance with orders to hand over confidential information from an email account belonging to the former soldier.

Both proceedings are in the Federal Court.

In a judgment delivered on Friday, Justice Robert Bromwich said Mr Roberts-Smith claimed Ms Roberts accessed his "RS Group Australia" email account, then passed on information for use in the defamation case.

"The crux of all this is that Mr Roberts-Smith believes that the notice to produce in the defamation proceedings was informed by confidential information of his that was provided to the respondents in those proceedings by Ms Roberts," Justice Bromwich said.

However, the judge said Mr Roberts-Smith failed to prove a "sufficient basis" to examine Ms Roberts over her delivery to the court of any information obtained from the RS Group email account.

He ruled that Ms Roberts accessed Mr Roberts-Smith's RS Group email account for a "legitimate purpose" after suspecting that Mr Roberts-Smith was having an affair with a female solicitor acting for him in court proceedings.

Ms Roberts had a number of WhatsApp exchanges with her close friend Danielle Scott about her suspicions, but the judge said there was "no basis" to claim that Ms Roberts gave Ms Scott, or anyone else, access to the email account.

Ms Scott, like Ms Roberts, is set to testify for the newspapers against Mr Roberts-Smith in the defamation trial, according to the judgment.

"Ms Roberts repeats her previous sworn evidence that she has never provided any person with access to Mr Roberts-Smith's email account," Justice Bromwich said.

"Ms Roberts has candidly disclosed the circumstances by which she came to have an image of the ... email."

The judge said there were also insufficient grounds to join Ms Scott, and her husband, to the action.

He said, in his view, Mr Roberts-Smith's case failed to go beyond "bare possibilities and suspicions, with many such assertions in relation to Ms Roberts being shown to be ill-founded".

Claims against Ms Scott were "equally ill-founded", the judge said.

"Both Mr Roberts-Smith's interlocutory application for the examination of Ms Roberts, and his interlocutory application to join Ms Scott and her husband must be dismissed," he ruled.

Mr Roberts-Smith's barrister Arthur Moses QC previously told the court that an email account used by Ms Scott or her husband accessed the war hero's password-protected account at least 101 times between January 20, 2020 and May 7, 2021.

Justice Bromwich ordered Mr Roberts-Smith to pay Ms Roberts' costs and adjourned the matter to January 28 for case management.

Australian Associated Press