Liberal strategist Mark Textor and former Liberal Party federal director Lynton Crosby are currently suing Mr Kelly, the former member for Eden-Monaro, for a tweet in October 2011 accusing them of introducing "push polling" to Australia.

The practice, considered morally questionable, uses loaded questions to try and influence respondents' views.

Dr Kelly's tweet read: "Always grate [sic] to hear moralising from Crosby, Textor, Steal & Gnash. The mob who introduced push polling to Aus."

Mr Textor and Mr Crosby allege the tweet defamed them, whil

Dr Kelly's defence, one of contextual truth, would allow him to escape liability if he is able to prove the pair were "hypocrites", and that the allegation outweighs any other defamatory meaning in the tweet.

The case has become bogged down in the Federal Court, running for four years without resolution.

It appeared back in the Federal Court on Wednesday before Justice Steven Rares, as the parties squabbled over the discovery of documents.

Mr Kelly is seeking campaign documents said to have been in the possession of Mr Crosby during federal campaigns, but alleges his lawyers have not complied with rules around disclosure.

The same accusation was levelled at Mr Kelly's lawyers by Mr Crosby's barrister Gillian Dempsey on Wednesday.

The matter is now on its way to mediation, the court heard, and a mediator is to be selected by mid-May.

Dr Dempsey said it may be difficult for Mr Crosby to return for the mediation, given his role in the British general election.

Justice Rares responded that it would be ideal to have him in the room, as "personality-driven issues" seemed to be at play.

"[This] is a matter that cries out for mediation and it would be good for the parties to sit down constructively," he said.

He also expressed a reluctance to further delay the case.

"This matter has been ongoing for four years and I don't think I should be pushing out dates."

He warned the broad nature of the issues raised meant it was likely to be expensive.