Business and industry groups are urging the Albanese government to go back to the drawing board on industrial relations laws after they cleared their first hurdle.
The laws, aimed at closing labour hire loopholes, went through the House of Representatives on Wednesday with 89 amendments.
However, the bill's path through the Senate remains uncertain.
The legislation will add guardrails for the Fair Work Commission on minimum standards for gig workers and clarify the definition of casual workers.
Australian Chamber of Commerce and Industry chief Andrew McKellar told reporters after the vote there was a "fundamental flaw" in the way the laws were being dealt with by MPs.
"We saw 89 new amendments being brought brought forth on top of 800 pages of existing legislation that was rammed through the House of Representatives," he said.
"The way it is being managed is beginning to cause real static in that relationship (between business and government).
"It is causing damage that is making it much more difficult in an environment where there are real risks for the Australian economy, where we see continued pressure in terms of rising costs on households and businesses."
Business Council of Australia chief executive Bran Black said the amendments made a bad bill worse.
"We are deeply concerned the government is pursuing a policy which will make finding casual jobs harder in the middle of a cost-of-living crisis, when many Australians choose that extra pay," he said.
"The changes to the definition of a casual employee are nothing more than tinkering at the edges and do nothing to fix the complex and confusing nature of the definition for workers or their employers."
Minerals Council boss Tania Constable said it would be a blow to the resources sector.
"We want to go back to the drawing board and work with government to get this legislation right."
Workplace Minister Tony Burke said the changes would lead to better workplace protection and industry groups had been consulted.
"The amendments are pragmatic, practical changes that ensure we avoid unintended consequences," he said.
The minister was unconcerned by the attacks on the laws by business groups and negative advertising campaigns.
"A lot of Australians seeing those ads would wonder why they don't just spend that money on properly paying their workers," he said.
The workplace laws will also contain three Greens amendments, after the government decided to back a proposal which included treating super theft the same as wage theft.
ACTU secretary Sally McManus said the changes would crack down on workers being disadvantaged.
"Politicians need to act with urgency to get the closing loopholes bill passed," she said.
"The public want action on wage theft and better job security - these simple measures will make a huge difference to workers right now."
