Federal Opposition Leader Bill Shorten's office has rejected an apology from the trade union royal commission for its decision to release documents clearing him of wrongdoing after 8:00pm on a Friday night.

Last week, the Royal Commission into Trade Union Governance and Corruption released a statement and chapters of submissions from its legal team, headed by Jeremy Stoljar SC, which cleared Mr Shorten of any unlawful conduct from his time as an official with the Australian Workers Union (AWU).

Labor and the Greens slammed the timing, calling it an attempt to avoid media scrutiny.

It led the commission to take the unusual step of releasing an email conversation between Mr Shorten's lawyer Leon Zwier and the commission's legal team.

In the email written on Sunday, Mr Zwier said he left messages for lawyers to call him back.

"I was seeking to understand the proposed timing of the release of Jeremy Stoljar's AWU submissions," Mr Zwier wrote.

"I am aware that TURC published a press release concerning Mr Shorten.

"Can you please explain why you chose not to send it to me on or before its release to the media."

The commission's lawyer James Beaton responded on Monday, apologising to Mr Zwier.

"[The submissions] were still being finalised on Friday evening and the team was working hard to get them out to all affected persons in accordance with the commissioner's published deadline," Mr Beaton wrote.

"We were conscious that like you, there were teams of lawyers around the country standing by waiting for them.

"The commission's sole objective in releasing the submissions on Friday evening was to meet a legal deadline and thereby honour its commitment to all affected persons who only have 14 days to respond with their submissions."

Mr Beaton said it was always clear the submissions would be released to the media.

He argued it was not common practice to provide media releases to legal representatives and offered to add Mr Zwier to their media distribution list.

A spokesman for Mr Shorten rejected the apology.

"Releasing information to the media at 8:00pm on a Friday night is a sure-fire way to bury news," the spokesman said.

"These actions say everything about how political this royal commission is.

"No reasonable person would think that withholding such significant news until late on a Friday is acceptable."