Workers amassing more than 60,000 have downed tools across the nation to march through capital cities to protest the federal takeover of the CFMEU.
Up to 50,000 Construction, Forestry and Maritime Employees Union members gathered outside Melbourne's Trades Hall as a rally got underway in the union's hometown on Tuesday.
A further 8000 gathered in Sydney, with around 4000 in Brisbane.
The number of protesters across the nation was higher than the population of Queensland's Hervey Bay.
Dressed in hi-vis and work gear and wielding signs such as "Hands off the CFMEU", protesters in Melbourne waved union flags as they shut down major roads around the CBD.
"When I say union, you say power," they chanted.
In Sydney, union members shut down Macquarie Street outside the NSW Parliament, shouting "union power" and "f*** Albo".
Deposed CFMEU NSW state secretary Darren Greenfield, who has denied allegations of corruption in court, attacked the peak trade union body, the ACTU, and its leader.
"Sally McManus is a sellout," he said as boos rang out.
"We pay her to look after us and she sold us out for the Labor Party."
In Brisbane, protesters flooded the CBD's Queen's Gardens forcing authorities to shut down nearby Elizabeth, George and William streets.
There were no arrests in either Sydney or Brisbane, with Queensland Police describing the rally as "peaceful".
The action comes days after after the union was placed into administration by Attorney-General Mark Dreyfus, amid allegations of links to organised crime and corruption in the construction arm.
The protesters risk being fined by the industrial watchdog if they abandon work to take part in rallies, as the action is unprotected.
In Brisbane, the marchers were addressed by federal Greens MP Max Chandler-Mather, who told them the government had established a blueprint on how to seize control of a civil movement or union.
"Labor has used these untested allegations to attack an entire union," he said.
"You will be dismissed as radicals ... but it's not radical to believe that a construction worker should be afforded a fair trial like a CEO, banker or a politician.
"The real radicals are the Labor and Liberal politicians on untested allegations who are doing this as judge, jury and executioner."
Electrical Trades Union leaders also addressed the marches in Brisbane, Melbourne and Sydney.
Queensland ETU secretary Peter Ong told protesters the Labor Party was not the union movement.
"This is the union, comrades," he said, gesturing to the large crowd.
"This is not an attack on the CFMEU, this is an attack on the trade union movement ... from what we thought was our own."
In Melbourne, ETU state secretary Troy Gray said the size of the crowd reflected workers both inside and outside the CFMEU.
Maritime Union national secretary Paddy Crumlin spoke in Sydney, labelling the government's action a "massive busting up of unions".
"This is an attack on every working man and woman," he said.
A Fair Work Ombudsman spokesperson said if a site worker failed to turn up or walked off the job without permission on Tuesday, it could be a contravention of workplace laws.
Earlier on Tuesday, Federal Treasurer Jim Chalmers urged protesters to be peaceful despite their opposition to how the past week has unfolded.
