Workers' rights will be set back significantly if the coalition wins power at the next election, the head of Australia's peak union body says.
The warning from ACTU president Michele O'Neil followed comments on Sunday from opposition finance spokeswoman Jane Hume indicating the coalition would review many elements of the federal government's industrial relations reforms.
Among the measures were laws allowing labour hire workers to be paid the same as employees, as well as multi-employer bargaining.
"We'll be reviewing industrial relations laws to make sure that we improve the productivity of our economy," Senator Hume told ABC's Insiders program on Sunday.
"Changing industrial relation laws from opposition is impossible, so of course it would happen in government."
Senator Hume also confirmed the opposition would examine laws which came into effect in August allowing employees to disconnect from work after hours, along with changes to casual employment that allows for workers to progress to a part-time or full-time position.
"We will redefine 'casual' back to its original definition because that is actually adding inflexibility to our workplace practices, not improving it," she said.
"The right to disconnect laws will need to be considered because quite frankly this is stuff to be negotiated between an employee and employer. These are unnecessary laws adding more complexity to our system."
The ACTU president said any changes to the industrial relations reform would be a backward step.
"(The coalition) intend to take away the rights that workers fought for a long time to win. They intend to take away rights that actually have been finally seeing a real increase in wages for workers," she told reporters in Canberra on Monday.
"We'd see a removal of multi-employer bargaining, which has finally given low-paid workers the right to be able to bargain them for better pay."
Ms O'Neil accused Opposition Leader Peter Dutton of backing large companies, rather than workers.
"The opposition is on the side of big business. They're on the side of people who want to cut pay and conditions," she said.
"What we want to see is workers continue to see the benefits of what have been really important changes in the last two years."