Rob and Fern Messenger brought action against the senator and Commonwealth Government after they were sacked in 2017, following a workplace complaint made against her to Prime Minister Malcolm Turnbull.

They argued at a Federal Court hearing on Friday former adviser Norbert Keough and journalist Annika Smethurst could provide evidence at trial on how the pair suffered adverse action following the complaint.

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Mr Messenger said Mr Keough would be able to explain why office staff provided alleged misleading information in statutory declarations provided as evidence for the trial.

He said Mr Keough would be able to submit examples seen and heard by him of adverse actions taken against he and his wife.

Mr Messenger, Senator Lambie's former chief of staff, said Mr Keough would be able to provide evidence that he was employed to replace him and Mrs Messenger.

Justice John Snaden ruled against the move for Mr Keough to be subpoenaed as the Messengers' argument overwhelmingly relied on speculation on what evidence might be given.

He made the same ruling in regards to hearing evidence from Ms Smethurst who was leaked their workplace health and safety complaint against Senator Lambie.

Mr Messenger attempted to argue as Ms Smethurst knew the identities of those who leaked the document she would be able to speak to their motivations for doing so, which he said was to cause them damage.

Commonwealth lawyer Christopher McDermott told the court the article was published some months after their alleged unfair dismissal.

Justice Snaden said he was not convinced Ms Smethurst could provide more than hearsay evidence.

"How could she say what the motivations were of those people without being one of those people?" he said.

A further case management hearing has been scheduled for September 2 at 9.30am. The trial is scheduled to start on September 21.

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