More than 50,000 workers have gathered outside Melbourne's Trades Hall to rally for better working conditions and a pay rise.
Australia's standard of living is going backwards, unions say, as thousands rally around the country as part of an ongoing national pay rise fight.
The ACTU estimates 150,000 people, including Premier Daniel Andrews, will rally in Melbourne and thousands more will join the call in Sydney, Darwin, Wollongong, Cairns, Townsville and at other regional centres demanding to be given a "fair go".
Protesters in Melbourne accused Prime Minister Scott Morrison of taking workers on a "highway to hell".
"We are fighting for our lives and a fair go," cleaner Rajita told reporters outside Trades Hall in Carlton before an AC/DC cover band performed for the crowd.
A sea of high-vis neon yellow and orange has now taken over the Melbourne CBD as workers march from Trades Hall to Federation Square.
ACTU secretary Sally McManus said the disruption was worth it.
"Our standard of living is going backwards. That should not be happening," ACTU secretary Sally McManus said in Melbourne on Tuesday.
"A small disruption for a couple of hours is worth it.
"There is an appalling figure that 28,000 working people are homeless in our country.
"That's because the minimum wage in our country is just $37,000 - that is not enough to support yourself."
As the rally prepared to get underway, CFMEU boss John Setka quoted historical figures in a tweet to justify the action, including Martin Luther King saying 'Never forget that everything Hitler did in Germany was legal,'.
Federal minister Kelly O'Dwyer accused him of comparing Hitler's Nazi Germany to Australia and said the comparison was "vile".
"John Setka has done it again. His vile slur against the Federal Govt (sic) likening it to the Hitler regime is beyond repugnant," she tweeted.
Premier Daniel Andrews planned to join the march, saying Victorians are working harder than ever but not being rewarded.
"They want a better deal, they're entitled to that, so they can provide the best for their kids and they can have a better standard of living and greater opportunities than their parents have had," he told reporters.
The Australian Chamber of Commerce and Industry has dismissed the union claims.
"Scratch the surface and the ACTU's campaign is really about putting power into the hands of big unions, disempowering employees, and removing their choices," CEO James Pearson said.