Ms McManus took to X, formerly Twitter, blaming self-serving leaders' failure to step down as the reason the union's construction and general divisions were placed into administration.
"Some members of the construction division of the CFMEU have had serious allegations levelled against them. We're not talking about small things," she said in a video posted to the social media site on Monday.
"We're talking about criminal activity, corruption, violence and intimidation.
"There have also been threats, harassment, assaults and abuse against workers and other union officials, and union leaders dealing with criminal figures, kickbacks and corruption."
What's going on and what we stand for — Sally McManus (@sallymcmanus) https://t.co/RCDz9tNYnPSeptember 9, 2024
Ms McManus said the ACTU asked the CFMEU to rid themselves of any criminal elements and for those accused of criminal activity to stand down until investigated.
She said doing this would have protected the organisation, but instead CFMEU leaders put their own interests before the union movement.
Again, the union leaders did not act when the ACTU asked them to voluntarily go into independent administration, Ms McManus said.
"This period of administration is about one thing - ridding the union of criminal elements, intimidation and violence," she said.
Reactions to the video were mixed, with some questioning Ms McManus's support of an administrator and government legislation enacted after the scandal erupted.
Others congratulated Ms McManus on her stance to rid unions of corruption.
The embattled Construction, Forestry and Maritime Employees Union had its construction and general divisions placed into administration after 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 the roles of more than 200 elected CFMEU officers were terminated.
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