Labor has warned proposed laws designed to shame Australia's largest companies into quickly paying debts to small businesses may not work.
Businesses with a turnover of more than $100 million would have to publicly display how fast they paid invoices to businesses with a turnover under $10 million.
But Labor says the bill, which passed the House of Representatives on Thursday night, doesn't dictate a time frame companies have to pay up.
The party's industry spokesman Brendan O'Connor pointed to laws overseas which penalise companies with interest rates after a set amount of days without payment.
"It is rather fanciful to suggest that transparency alone will change the culture of payments by larger businesses to smaller businesses," he told parliament.
The opposition wants a Senate committee to review the bill.
The register would be run by a government watchdog and list payment times in brackets of 21 to 30 days, 31 to 60 days and more than 60 days.
But with most large businesses failing to pay after more than 120 days, Mr O'Connor said the register would hide the worst offenders.
"It is incumbent on the Senate to review this bill's efficacy and shortcomings in a constructive way," he said.