Abbott challenges Shorten over union ties

Prime Minister Tony Abbott says Bill Shorten must answer questions about whether Australian Workers Union members were "ripped off".

Cesar Melhem, who succeeded Mr Shorten as Victorian state secretary of the AWU, on Tuesday stepped aside as a government whip in the Victorian parliament.

Mr Melhem has denied allegations stemming from the unions royal commission that he dudded cleaners out of $2 million in penalty rates in return for $25,000 a year in donations.

Asked whether he would distance himself from Mr Melhem, Mr Shorten told reporters in Hobart on Wednesday: "I have made it clear that it doesn't matter who you are, if you engage in corruption in the workplace, employer or union rep, you should feel the full force of the law."

Mr Abbott said Mr Shorten had refused to answer questions about his time as AWU boss.

"He's very familiar with the union business model and what we've learnt from the royal commission over the last few days is that the AWU in particular was guilty of ripping off workers to advance its own political position," Mr Abbott told reporters in Sydney.

"Mr Shorten has questions to answer and it's just not good enough for him to stonewall in the face of perfectly reasonable questions about whether these sorts of sweetheart deals were done in his time as a union leader."

The Labor leader said he would not provide a running commentary on the royal commission.

"In my time working as a union official, I have always put the interests of my members first every time," he said.

Mr Shorten was briefly mentioned in evidence at the commission in September last year in relation to the company Chiquita Mushrooms, which paid the AWU $4000 a month for training from September 2003 to January 2004.

The commission found the money did not go into a training account but rather the union's "general revenue stream".

However the company's human resources manager told the inquiry his discussion with Mr Shorten, as the-then secretary of the Victorian AWU, in 2003 was limited to the number of contractors on site and the enterprise bargaining agreement.

While the time limit for any civil court action had expired, the commission found the payments had been made "for no legitimate purpose".