Crucial crossbench senators Pauline Hanson and Jacqui Lambie have demanded the government release its proposed changes to union-busting laws.
If either of the pair support the "ensuring integrity" bill the government will be able to pass the laws, which make it easier to deregister unions and ban officials.
Attorney-General Christian Porter said the government would release the amendments shortly, but not while negotiations with minor parties and independents were ongoing.
He's confident the bill will pass in parliament's final sitting fortnight of the year, which starts on Monday, despite the fresh crossbench angst.
Tasmanian independent Senator Lambie has warned she won't support the bill without giving unions, bosses, lawyers and the public a say on the government's amendments.
"You don't end the career of a union official or cancel the registration of a union on a lark," she said on Wednesday.
"You've got to know the consequences. And by hiding these amendments behind the silly excuse of 'They're still being finalised' is taking us for fools."
Labor seized on Mr Porter promising to shortly release the amendments after the minister rejected the opposition's demands earlier in the week.
"Every day he refuses to release these amendments is another day he dodges proper scrutiny," opposition industrial relations spokesman Tony Burke said.
Senator Hanson said unions had raised a number of genuine concerns about the bill in its original form, calling for the amendments to be released as soon as possible.
"I won't stand for union bashing and therefore I won't support the deregistration of organisations for misdemeanour offences like late paperwork submissions," she said.
"I have however forewarned union bosses that bullying and thuggery must be stamped out in accordance with public expectations."
Centre Alliance's Rex Patrick proposed a demerit point system, which is understood to have been included in the government's changes to the bill.
Unions argue despite the demerit point system, the bill will allow deregistrations and disqualifications to occur for minor paperwork breaches.
Mr Porter dismissed those claims, insisting suggestions the laws could be weaponised against unions were nonsense.
"This view that's been put out there that a nurses' union could get deregistered for a minor breach of industrial law is just wrong. It's just fanciful," he told the National Press Club.
He said the legislation was critical to addressing "off the charts" lawlessness in the CFMMEU, noting Senator Lambie promised to back the bill unless Victorian secretary John Setka quit.
Australian Associated Press