Bill Shorten will be quizzed on “ghost” union members and deals struck with construction companies when he faces the royal commission on Wednesday.
The former Australian Workers Union national secretary will be the third Labor leader, after Julia Gillard and Kevin Rudd, to appear at two royal commissions initiated by Prime Minister Tony Abbott.
Ms Gillard appeared at the unions inquiry and Mr Rudd faced questions in the home insulation commission.
Mr Abbott told reporters in Sydney on Tuesday the evidence of previous witnesses showed there were a lot of “ghosts” on union membership rolls and deals had been done to “dud” workers.
“Let’s see what light can be cast on that in the next day or so,” he said.
Labor workplace spokesman Brendan O’Connor told AAP the prime minister had his own questions to answer.
“Why has the prime minister set up two royal commissions (the second being the home insulation inquiry) and summoned three Labor leaders to those commissions?” he said.
“Why has he spent $80 million of taxpayers’ money going after his political opponents, and wouldn’t that money be better spent on health and education services?”
Mr Abbott said the aim of the inquiry was to deliver “honest unions”.
Mr Shorten has been briefly mentioned in evidence during the inquiry in 2014 and 2015.
He has provided several affidavits to the royal commission.
In one affidavit, Mr Shorten denies a 1996 conversation in which he was alleged to have told former AWU Victorian president Bob Kernohan “we are all just moving on” when discussing the recovery of some worker redundancy payments.
In another, he does not recall discussing a “paid education leave” arrangement negotiated with the company Chiquita Mushrooms in 2004.
Mr Shorten is also expected to be asked about the legitimacy of companies paying the union dues of workers and funding AWU-run training programs.
Mr O’Connor said any allegations of criminal conduct were better dealt with by police and the Australian Crime Commission.
“It’s spurious to suggest there is endemic corruption to warrant spending so much money on these matters,” he said.
“Whatever is put to him, you will see in Bill a person who for most of his adult life worked in defence of wages and conditions and job security for workers.”
The royal commission’s final report is due by the end of the year, after the government extended its hearings.
Meanwhile, a video has emerged of Mr Shorten delivering a passionate speech about Labor values to a pub crowd.
In the video posted on YouTube, Mr Shorten outlines to noisy patrons at Sydney’s Covent Garden Hotel on Sunday night his vision for a country where “people can organise to have a strong minimum wage and will not be subject to a royal commission”.