Geneva-based Ms Burrow, who travelled to Canberra on Thursday to receive her Companion of the Order of Australia and lobby the Senate crossbench to vote against the government's union-busting bill, said the level of wage theft in her home country was "unbelievable".

"Frankly, until you see some serious sanctions on people who engage in taking money from workers, then it is in fact a form of wage slavery and again it's unbelievable that it happens right here in Australia where you have a robust rule of law," the International Trade Union Confederation's general secretary said.

"The theft of wages in this country is akin to the kind of conditions we see in countries like the Gulf states where the kafala system [of migrant workers] exists."

Industrial Relations Minister Christian Porter is drafting a bill to impose criminal sanctions on employers who engage in systemic wage underpayment, but unions are concerned the threshold for criminal conduct may be set too high.

Australian Council of Trade Unions president Michele O'Neil said wage theft was "endemic" and politicians should focus on fixing it instead of cracking down on unions with its Ensuring Integrity Bill. The bill, which passed the lower house last month but is subject to a Senate inquiry, would make it easier to deregister unions and ban officials who broke the law.

Independent senator Jacqui Lambie, who holds a crucial swing vote on the bill, last week said she'd try to stop it going ahead if controversial union leader John Setka agreed to resign. Asked if Mr Setka should step down to appease Senator Lambie, Ms Burrow, a former ACTU president, said the issue was "not about one person".

"We would say to all the senators: 'This is not about a democratic Australia. It is a vendetta from a government who wants to take away workers' power, workers' rights to defend themselves and to create a decent Australia," Ms Burrow said. "Please, don't let it through the Senate."

The government needs the support of either Senator Lambie or Centre Alliance, which controls two Senate votes, to pass the bill. Centre Alliance senator Rex Patrick has said he will support it only if persuaded it achieves "parity" in the law's treatment of union and corporate leaders.

Employer groups are urging the Senate to support the bill to stamp out union corruption and workplace law breaches, including bullying on construction sites.

Mr Porter, who has previously said he is willing to negotiate on some aspects of the bill to secure Centre Alliance's support, said in question time on Thursday that it was "not just about the actions of John Setka". He said the bill "simply establishes there needs to be reasonable standards for people to hold public office in employer and employee organisations". Mr Setka has been under pressure to resign since pleading guilty in June to harassing his wife.

Workplace law expert Anthony Forsyth, a professor at RMIT University, said in a submission to the Senate inquiry ahead of his appearance at a Brisbane hearing on Friday, the bill would subject union leaders to higher standards than those faced by company directors.

Professor Forsyth said the government was "cherry picking" aspects of corporate regulation while "ignoring others" and the bill created "much broader grounds for disqualification" of union officials than those applicable to company directors. "There is no Corporations Act equivalent to the proposed fit-and-proper person test for union officials," he said.