Victorian Premier Jacinta Allan said she has referred ex-CFMEU boss John Setka to Victoria Police after he spoke to about 700 workers at a Metro Tunnel project site on Thursday morning.
It comes after Setka addressed workers at Footscray Hospital, which is undergoing a $1.5 billion revamp, on Wednesday.
"There is no place for John Setka on these worksites," Ms Allan told reporters.
"He was on the sites unlawfully and that is why the matter has been referred to Victoria Police for their further investigation.
"In terms of who attends work sites there are well-established processes here and it is the government's expectation that those building industry companies manage this process appropriately, which is clearly not what happened in these incidents over the past 24 hours."
Setka launched into an expletive-laden criticism of the state and federal governments during his visit to the hospital build site in Melbourne's west.
"People sort of asked why I resigned and I'm going to be honest with youse, f*****g Albo, and his f***ing bullshit," he told workers.
Setka, who quit in July after allegation bikies and underworld figures had infiltrated the union, gave insight into how his resignation took place: "They want a scalp you tell them I'll go. I'll resign right now. I'll resign tonight."
"My job is to protect the union and its members. I'm going to be gone in a few months," he told the crowd.
The Victorian government has asked construction giant Multiplex, which is managing the project, how the on-site rally unfolded.
Former CFMEU officials have launched a High Court challenge over its forced administration. (Darren England/AAP PHOTOS)
The Fair Work Ombudsman said it was investigating allegations former CFMEU officials have attended construction sites and encouraged those with information to come forward.
Victoria Police has been contacted for a response.
Federal Opposition leader Peter Dutton said Setka had "stunning audacity" to enter a second worksite.
'John Setka's worked out as well that Anthony Albanese is a weak leader," Mr Dutton told reporters in Sydney.
"They (the CFMEU) trade in misery. They go onto building sites, which forces up the cost of building."
Meanwhile, unions are banding together to support a High Court challenge after the CFMEU was placed into administration.
The Maritime Union of Australia will join other trade unions to help fund the CFMEU's legal battle, claiming the government's decision was "unjustified, chaotic and reckless".
The Maritime Union said the government's move against the CFMEU was "unjustified and reckless". (Joel Carrett/AAP PHOTOS)
It could jeopardise progress on enterprise bargaining agreements, send a green light to "bad and abusive employers" or set a precedent for moves against other unions based on "untested media allegations", the maritime workers' group warned.
"We are supporting ... and backing them in as they fight for the right of their division to exist," the Maritime Union of Australia said.
"We are also concerned by the near certainty that similar future legislation will be used by governments of either stripe against other militant blue-collar unions, including the MUA.
"We have been on the receiving end of these calculated political and media smears in the past and will support our fellow members ... as they seek to clear their names and fight for the principles of natural justice, presumption of innocence, the rules of evidence and procedural fairness."
The embattled CFMEU had its construction and general divisions placed into administration after the corruption allegations prompted the federal government to try to rein it in.
Laws to bolster this effort passed parliament in August and gave the relevant minister powers to intervene and slap life bans on CFMEU officials.
Mark Irving KC was appointed as administrator and more than 200 elected CFMEU officers had their roles terminated immediately.
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