A major employer body is ramping up pressure on crossbench senators to pass draft laws making it easier to disqualify rogue unions and their officials.
Australian Industry Group chief executive Innes Willox has written to the pivotal mixed bag of senators, urging them to vote for the coalition's Ensuring Integrity Bill.
Mr Willox said giving beefed up powers to the Federal Court would provide the Construction, Forestry, Maritime, Mining and Energy Union with a strong incentive to stop breaking the law and treating fines as a business cost.
"The CFMMEU's repeated law-breaking is unacceptable and cannot be allowed to continue," Mr Willox wrote.
"Numerous respected judges have expressed dismay at the blatant disregard that the CFMMEU has for the rule of law."
The influential business leader said the union had been fined more than $16 million in the past decade, without a noticeable impact on its financial strength or unlawful conduct.
The legislation would allow the court to deregister unions for repeated breaches of industrial laws or corrupt conduct by officials.
Prime Minister Scott Morrison has signalled he's not afraid to take on unions, returning the industrial relations portfolio to cabinet and threatening to deregister the construction union.
New Industrial Relations Kelly O'Dwyer has described the bill as critical to protecting workers, reviving it after it was shelved in March when the government failed to win Senate support.
The reforms would also create a public interest test for union mergers, like the amalgamation which brought the maritime and textile unions into the CFMMEU.
ACTU president Michele O'Neil is in Canberra, lobbying independent and minor party senators to vote against the measures.
"This bill will make a broken system worse and gives even more power to big business," Ms O'Neil said.
Unions and their members should be able to decide how they are run, she said.
"No ministers or business lobbyists should be able to undermine a union's capacity to protect working people's safety and win fairer wages and better job security," the ACTU president said.
Australian Associated Press