Bill Shorten has slammed the trade union royal commission over its late night release of a statement effectively clearing him of any wrongdoing while he was a union boss.

The commission announced late on Friday that there was "no submission that Mr Bill Shorten may have engaged in any criminal or unlawful conduct" from the inquiry's lawyers.

Labor says the opposition leader was only told he had been cleared when he was contacted by journalists, who received hundreds of pages of submissions after 8pm.

The late night release missed many media deadlines, sparking suggestions the commission tried to bury the story.

Mr Shorten said on Saturday the political nature of the commission had been exposed.

"If something is coming out at eight o'clock at night, I'm not going to speculate, but it does speak for itself," Mr Shorten told reporters in Perth.

The commission has issued a statement insisting the submissions were released to all those affected before being provided to the media, within a timetable set by Commissioner Dyson Heydon in October.

It said staff worked under "great pressure" to meet the deadline and that "there was no disrespect intended to any affected person by this process".

Mr Shorten rejected the explanation, saying commission staff are being paid millions to do their jobs.

"If you were being paid millions of dollars to write a report, do you think you'd be able to do it within a time line and not rush it at the last minute?"

Mr Shorten appeared before the royal commission over two days in July to answer questions about his time as head of the federal and Victorian branches of the Australian Workers' Union before he entered parliament in 2007.

Senior Labor figure Brendan O'Connor is demanding the federal government apologise for wasting $80 million of taxpayer funds on a "witch-hunt" designed to smear its political opponents.

"What sort of proper process could possibly be in place to have to hear about whether you've been cleared from the media?" Mr O'Connor told journalists in Melbourne.

"This has been an improper process from beginning to end."

The government kept quiet on Saturday.

Liberal frontbencher Scott Ryan refused to comment on Mr Shorten's case but defended the royal commission, telling Sky News it had illustrated systemic failures in the oversight of parts of the union movement.

Greens leader Richard Di Natale said former prime minister Tony Abbott should hang his head in shame for setting up a royal commission that has been revealed as a "stitch-up".