Businesses have been warned "time's up" under a labour hire sector overhaul by the federal government aimed at protecting the pay and conditions of workers.
The changes to workplace laws, introduced to parliament on Monday, have been labelled as "radical" and "unworkable" by industry groups.
The government says the reforms will close loopholes, including the use of labour hire workers to undercut the agreed rates of pay for employees.
The reforms also seek to criminalise wage theft, bolster protections for gig workers and create a pathway for casuals to become permanent.
Workplace Relations Minister Tony Burke said the changes will apply to a fairly small group of firms doing the wrong thing, with the majority of workers and businesses unaffected.
"Anyone who has been underpaid, today's a good day for them," he told Nine's Today program on Tuesday.
"Wage theft will be a crime.
"We'll get some minimum standards in the gig economy and businesses that have been using the labour hire loophole to undercut rates ... they know time's up.
"For a limited number of businesses in areas that have been posting pretty healthy profits, their workers will earn a little bit more."
Mr Burke also said his engagement with crossbench MPs on the legislation was "good".
"The Senate crossbench, we're having good conversations. We'll talk to them in good faith," he said.
But business groups, which have been campaigning against the changes for several months, are wary of the scope of the reforms.
Master Builders Australia, which represents the building and construction industry, challenged the notion the reforms would have a minimal impact.
"There is nothing simple about adding hundreds of pages to the Fair Work Act and expecting businesses of all sizes and independent contractors to try and navigate it," chief executive officer Denita Wawn said.
The Australian Retailers Association raised concerns about the changes for casual workers.
"We see the benefits of a more permanent retail workforce, but our members say there are currently very low levels of casual conversion," ARA CEO Paul Zahra said.
Greens leader Adam Bandt said his party wanted more money going into workers' pockets, but the party is yet to say whether it will support the legislation or not.
The Greens party room will meet on Tuesday to consider the reforms.
"We've been pushing for some years now to ensure that there's a hard floor underneath Australian labour laws so that people can't be exploited and paid less than the minimum wage," he told the ABC's RN.
Mr Burke challenged anyone opposing the changes to defend the loopholes.
"If someone thinks it's reasonable, that wage theft should not be a crime, defend it," he said while introducing the bill to parliament on Monday.