Labour hire providers in Queensland are now legally required to be licensed or have applied for one.
New laws passed by the state government earlier this year came into effect on Friday.
Queensland Council of Unions general secretary Ros McLennan said the sunshine state was the first jurisdiction in Australia to regulate the sector.
"Before these laws it was easier to start a labour hire firm than getting your licence to drive, and that wasn't right," she said in a statement.
"We've heard shocking stories of workers on labour hire arrangements being underpaid thousands and thousands of dollars across all sorts of industries and sectors, and it's got to stop."
Ms McLennan called on other states to introduce similar laws so rogue operators could be stamped out.
"The impact on law-abiding businesses will be negligible, as the reporting requirements should not be onerous for an organisation complying with the law," she said.