Geoffrey Watson SC, whose report into the CFMEU triggered a royal commission in Queensland and led to the downfall of a Victorian premier, said he was losing money after his sixth and last day on the witness stand.
Under fierce questioning from Ruth O'Gorman KC, for former Queensland union official Michael Ravbar, Mr Watson reminded the inquiry that he was there voluntarily.
"I'm not subject to this jurisdiction here," he said.
"Every time I come, it costs me money."
Ms O'Gorman had challenged Mr Watson over his description of the CFMEU's payment of personal fines for its members as proof of what he characterised as the CFMEU's lawlessness in his report.
Earlier, Mr Watson had sparred in even more spectacular fashion with Simon Wilson KC, for the M1 Trades Group.
Mr Watson had alleged that M1 Traffic Control QLD Pty Ltd, owned by Michael Portia and Tony Paragalli, was in fact controlled behind the scenes by Melbourne associate Mick Gatto.
Both Mr Portia and Mr Paragalli vehemently denied the claims in an affidavit.
Mr Watson read out a list of a dozen shell "M" companies that he said were intended to disguise Mr Gatto's involvement for taxation purposes.
Exchanges between Mr Watson and Mr Wilson became so heated that Commissioner Stuart Wood KC advised them to cool off ahead of the morning tea adjournment.
"Both you and Mr Watson are very experienced silks, you know what the rules of engagement are," he told Mr Wilson.
"After the break, I think we should try to apply those rules of engagement in an orthodox manner."
After the lunch adjournment, Mr Watson recanted on his threat not to return to the inquiry, saying he would do so if summonsed.
Mr Wood acknowledged that Mr Watson had had a trying morning.
"You've devoted a lot of time from your sense of public service to this commission, and we're grateful for it," Mr Wood said.
Mr Watson also told the inquiry the Victorian government never contacted him about the explosive contents of his report Rotting from the Top, which led to the downfall of former premier Jacinta Allan this week.
The report exposed the exploitation of Victoria's Big Build by the CFMEU, in collaboration with some of Melbourne's most notorious underworld figures.
Ms Allan's Labor government had been publicly critical of Mr Watson following the release of his report which detailed corruption surrounding its Big Build, a $100 billion construction project that began under former Victorian premier Dan Andrews.
Mr Watson estimated the alleged corrupt conduct by the CFMEU and Mr Gatto, a self-styled construction industry "mediator", had effectively fleeced Victorian taxpayers of $15 billion.
Asked by counsel assisting Patrick Wheelahan KC if Ms Allan's government had spoken to him about his report, Mr Watson said nobody from the Labor Party had  contacted him to discuss that.
Ms Allan's successor Ben Carroll announced the Victorian government would hold its own royal commission into the construction sector and the CFMEU at his first press conference as premier.
Earlier, CFMEU administrator Michael Crosby said his goal was to regulate the construction sector "so that we wipe out the opportunity to make illegal money out of the industry".
Mr Crosby has given former Victorian CFMEU boss John Setka until August 7 to explain why he should not be expelled from the union following allegations of threatening behaviour.
"It's the construction industry, and organised crime wants a cut of it. That's the reality," he told ABC radio.
