Coercive powers that force builders and construction workers to give evidence about workplace misconduct will continue.
Legislation to extend for two years powers that force a person to hand over documents or testify to the industry's regulatory body passed the Senate on Monday with crossbench support.
Employment Minister Eric Abetz said the "stop-gap" measure gave witnesses the excuse of legal compulsion to avoid intimidation for testifying.
It comes amid allegations of bullying by union officials, including members of the Construction, Forestry, Mining and Energy Union.
Labor fiercely opposed the bill, even though in the past it has supported it.
A 2003 royal commission into the industry found the coercive powers were necessary to penetrate the "veil of silence" behind which illegal industrial actions are hidden.
The government wants the powers to continue while it tries to convince the parliament to re-establish the Australian Building and Construction Commissioner, abolished by Labor.
But Labor frontbencher Doug Cameron said the extension was an attack on workers and pre-cursor to "extremist industrial legislation".
He believes the powers unfairly single out construction workers and impose on them tougher conditions than other employees.
The legislation still has to pass the House of Representatives where the government has the numbers.