Victorian Industrial Relations Minister Natalie Hutchins says it would be a travesty if CUB got away with using labour hire firms to reduce pay and conditions.
Thousands of union members have rallied in Melbourne in support of 55 sacked Carlton & United Breweries maintenance workers who refused to reapply for their positions with a new contractor offering reduced pay and conditions.
The workers claim CUB is gaming the Fair Work Act by trying to employ them via a new labour hire firm on a vastly inferior enterprise agreement.
"CUB needs to re-employ these 55 workers on the existing terms and conditions," ETU Victoria secretary Troy Gray told the rally outside parliament after supporters had marched from AFL House.
The AFL is sponsored by CUB and the union wants the league to boycott the company's beer during the upcoming finals series.
Mr Gray on Thursday said labour hire was "an absolute scourge".
"It's becoming the mainstay (but) it's insecure employment," he said.
"The big end of town ... use labour hire contractors and companies to avoid their responsibilities under the Fair Work Act."
The union boss said the federal legislation had to be changed and called for a Senate inquiry into "the corporate evasion of the Fair Work Act".
Victorian Industrial Relations Minister Natalie Hutchins told the crowd that while CUB argued the maintenance workers weren't their employees "I also know that CUB can't produce beer without them".
"CUB has been a prominent brand in Victoria and to let this company get away with what they've done to these workers would be a travesty," Ms Hutchins said.
Former independent federal MP and current Melbourne Lord Mayoral candidate Phil Cleary told the rally that "contract labour is an act of bastardry".
"It's the reason for the great strikes of the 1890s," he said.
"It's an act of brutality and contempt by CUB."
Mr Cleary called on AFL players Brent Harvey and Heath Shaw, as well as ex-champion Chris Judd, to join a boycott of CUB beer at the upcoming AFL finals.
Supporters of the beer workers also rallied in Brisbane on Thursday.
A CUB spokeswoman said claims the beer giant had sacked the 55 workers were false.
"CUB has not employed maintenance workers since 2009 - we changed contract providers earlier this year," she said in a statement.
"We believe this dispute is about unions wanting to enforce their power over an external company and the wages being offered."
The spokeswoman said CUB was still brewing beer at Abbotsford and had sufficient supplies for the footy finals.
"If that changes we would of course let our customers and drinkers know."