'Helpful' if Shorten fronts inquiry: PM

Prime Minister Tony Abbott says it would be helpful for Labor leader Bill Shorten to appear before a royal commission and explain his role in union deals.

Tony Abbott says it would be helpful for Bill Shorten (pic) to appear before a royal commission. (AAP)

The prime minister wants Bill Shorten to front the royal commission on union corruption to explain so-called sweetheart deals while he was head of the Australian Workers Union.

Tony Abbott says the Labor leader had "some explaining to do" after evidence to the commission revealed low-paid workers had been "ripped off so that union officials can flourish".

"I certainly think it would help if he would front the royal commission and clear things up," Mr Abbott told reporters in Melbourne on Friday, stopping short of echoing Jeff Kennett's calls for Mr Shorten to resign.