A report into the alleged infiltration of the CFMEU by bikie gangs has found the construction union's efforts to rid itself of criminal elements were "inadequate".

The union's construction arm was placed into administration in August following allegations outlaw motorcycle gangs had infiltrated its branches, with bikies allegedly appointed as delegates on major projects, amid wider claims of bullying, intimidation and corrupt conduct.

A report commissioned by CFMEU leadership and carried out by respected barrister Geoffrey Watson SC has found bikies were still influential within the union and that EBA negotiations had become "vulnerable to corruption".

The report's interim findings were released today by the union's administrator.

"On the information available to me, I consider that the Victorian branch has been infiltrated by OMCGs [outlaw motorcycle gangs] and by organised crime figures," Mr Watson said in his report.

"The Victorian branch has been caught up in a cycle of lawlessness, where violence was accepted as part of the culture, and threats of violence were a substitute for reasoned negotiations.

Mr Watson said during the course of his investigation, serious threats were made against CFMEU officials who were seen to be co-operating with the investigation.

He found union branch officials had not only engaged in threatening and abusive behaviour, they had also been subjected to threats, violence or abuse.

Mr Watson made seven recommendations, including that the CFMEU build co-operative relationships with police to deal with criminal conduct.

He also recommended further investigation into links with bikie gangs, a review of EBA processes, and the process by which union delegates are appointed.

Mr Watson also recommended an investigation into a specific allegation that union official Derek Christopher received around $200,000 in free labour and supplied from building companies in 2017.

Federal Workplace Relations Minister Murray Watt said the findings of the report backed up the government's decision to put the union into administration.

"This report was actually commissioned by the national secretary of the CFMEU, Zach Smith. So even a report commissioned by the union itself has demonstrated widespread corruption, widespread intimidation by bikies and widespread violence connected to the CFMEU and the construction industry," he said.

Mr Watt defended Prime Minister Anthony Albanese's response to revelations of alleged criminal infiltration of the CFMEU.

"No-one in Australian politics has stood more strongly against the CFMEU leadership, that unfortunately allowed violence and links to organised crime to go on, than Anthony Albanese," he said.

Police are continuing to investigate eight matters in relation to alleged fraud within the building industry, but have dismissed 12 other allegations.

Investigations continued into alleged intimidation of a developer, and a man had been charged over a separate allegation of threats to assault two owners of a labour hire company.

Last week, police said former CFMEU boss John Setka would not face trespass charges after he appeared at two construction sites in Melbourne.

Video emerged of Mr Setka delivering a speech to workers at the Footscray Hospital site and there were reports that he attended Metro Tunnel construction sites.

Premier Jacinta Allan described Mr Setka's presence at the workplaces as unacceptable and unlawful, but Victoria Police said it had not detected any criminal offences.

The Fair Work Ombudsman said earlier this month it was investigating whether Mr Setka's reported actions breached the Fair Work Act.