Kristina Keneally, a mainstay of Labor's federal election campaign, is among a cast of politicians who will break from campaign duties to give evidence in Greens Senator Sarah Hanson-Young's defamation case against David Leyonhjelm in the days before the election.
Senator Hanson-Young is suing for defamation over a series of comments the former Liberal Democratic Party senator made after a heated parliamentary debate last year about violence against women, during which he told the Greens senator from the sidelines to "stop shagging men".
Senator Hanson-Young's barrister, Sue Chrysanthou, told the Federal Court on Wednesday that "a number of [witnesses] ... are campaigning in their electorates" and foreshadowed an application would be made for them to give evidence via audiovisual link.
But Justice Richard White said "Senator Keneally is NSW-based" and the witnesses had known about the April 29 trial date for some time.
"You might have some persuading to do," he said.
The court heard Senator Hanson-Young intended to call five senators, including Senator Keneally, to give evidence in the five-day trial.
A former NSW premier and TV presenter, Senator Keneally is a key figure in Opposition Leader Bill Shorten's campaign for the prime ministership and is expected to be promoted into cabinet should Labor win the May 18 poll.
Mr Leyonhjelm, a former Liberal Democratic Party Senator who lost his bid for a NSW upper house seat in the March state election, intends to call Senators Derryn Hinch and Stirling Griff to give evidence. Both men had previously declined to cooperate with Mr Leyonhjelm's lawyers.
Senator Hanson-Young is not suing over Mr Leyonhjelm's comments in Parliament - which are covered by parliamentary privilege - but their repetition and expansion outside the Senate to Sky News' Outsiders program, the ABC's 7.30 program and Melbourne radio station 3AW, paired with a media statement posted on blogging website Medium.com.
Senator Leyonhjelm has said his "stop shagging men" comment in the Senate in June last year was in response to an alleged claim by Senator Hanson-Young that "all men are rapists". She denies making that claim.
In a statement of claim, lawyers for the Greens senator argue Senator Leyonhjelm defamed her by suggesting she made that "absurd" claim in Parliament.
They also say his comments paint her as a "hypocrite" in that she "claimed that all men are rapists but nevertheless had sexual relations with them", and a "misandrist, in that she publicly claimed that all men are rapists".
Senators Keneally, Hinch and Griff, among others, are expected to be asked what they heard during the Senate debate last year.