Flyers for Sin City in Surfers Paradise promise contestants the chance to "win a boob job valued at $10,000," although the fine print clarifies the prize is really cash for any use.
But since the ad suggests the money be spent on plastic surgery, it may violate Queensland's ban on promoting cosmetic surgery as a prize, the Sydney Morning Herald reports.
"This promotion may be a breach of that regulation and the matter has been referred for further investigation by the Office of Liquor and Gaming Regulation," the Office of Fair Trading said.
New laws also prohibit using "small print and disclaimers as an excuse for misleading or deceptive conduct."
Evonne Miller, a "body image expert" at Queensland University of Technology, blasted the promotion as "extremely sexist."
"We don't see any advertising for a $10,000 penis enlargement," she said. "It really highlights the double standard in society."
Craig Layt of the Australasian Society of Aesthetic Plastic Surgery lamented the "trivialization" of cosmetic surgery.
Sin City is promoting the prize at an "Ibiza-style" night April 3.