Geoffrey Watson SC's scathing report Rotting from the Top exposed the exploitation of Victoria's "Big Build" by the CFMEU, in collaboration with some of Melbourne's most notorious underworld figures.
It also triggered a Queensland inquiry into the CFMEU which continued on Friday with Mr Watson returning to the stand for his final appearance.
Mr Watson gave evidence just days after Victorian premier Jacinta Allan stood down following enormous pressure to commission to call an inquiry following his report.
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 Mick 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 has contacted me at all to discuss that.
"They made these statements to the press without asking me anything about how I arrived at the report and they were bitterly critical remarks.
"It's hard to read (those remarks) as being any less than they were suggesting I made it up."
He later accused the Victorian government of character assassination, saying statements by the then Victorian premier, police minister and attorney-general were "just awful".
"The police minister even had the temerity to say, if I had a problem, why didn't I go to the police," Mr Watson said.
"Oh, by the way, police minister, did you? Because if you had, you would have found out from your police force that I was going to them every week."
Ms Allan had previously claimed Mr Watson had backed down on the claims in his report, which he rejected.
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.
Mr Watson will face cross-examination later on Friday.
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".
"You can clean up the union, but if the rest of the industry isn't clearly regulated this is going to repeat sometime in the distant future and we just can't afford to have that happen again," he told ABC Radio.
"It's the construction industry, and organised crime wants a cut of it. That's the reality."
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