The commission has issued a statement saying Mr Heydon will announce his decision at 10am on Friday, and publish his reasons online "as soon as possible thereafter."

The commissioner – who has been accused of creating the apprehension of bias - was scheduled to deliver his decision on Tuesday, but on Monday afternoon delayed this without issuing a new timeframe.

Lawyers for unions that have appeared before the commission argued last week that the former High Court judge should disqualify himself following revelations he had agreed to speak at a Liberal Party fundraiser.

Prime Minister Tony Abbott and Opposition Leader Bill Shorten have both said the commission can continue under another commissioner if Mr Heydon steps down.

Despite later cancelling his appearance, the ACTU's barrister, Robert Newlinds, said on Friday that the "hypothetical observer" would think Mr Heydon harboured a political prejudice against the union officials before him.

Mr Newlinds also said he had not received all relevant documents, including emails, relating to the arrangements for the event, as the commission had promised.

Mr Heydon was billed as a speaker on an invitation to the event, which was named after former High Court Justice and Liberal MP, Sir Garfield Barwick.

He previously told the commission that he was asked to speak at the event last year, before the commission was extended for a year.

But he later "overlooked" the Liberal Party's connection to the event when he received a follow-up email in March this year and the fact he had only agreed to speak if the royal commission had finished its hearings at the time of the event.

Mr Heydon had not read an attached donation form and flyer he received on the event in June, as he had been busy with royal commission hearings.

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