Senate playmaker Jacqui Lambie has tightened the screws on construction kingpin John Setka as an upper house committee looks at union-busting legislation.
The crucial Senate swing voter said Mr Setka was doing more harm to the union movement than any laws ever could.
"If you want an electable ALP you should want him gone. If you want a strong union movement you should want him gone. Members, leaders, politicians want him gone," Senator Lambie said on Friday.
Mr Setka was suspended from Labor after being accused of bringing the party into disrepute, but is refusing to resign as head of Victoria's construction union.
"So if one union official can overrule everybody else and fail to put the interests of the movement above his own, and nobody can stop him, then we need laws to compel him to leave," Senator Lambie said.
"He's a billboard for the problem."
The Morrison government has seized on the controversy surrounding Mr Setka to revive legislation aimed at banning rogue unions and their officals.
Senator Lambie said Mr Setka faced a choice between the Morrison government's industrial relations laws, or his leadership.
"If he stays, the union movement is weakened. The leadership is weakened. The political arm is weakened," Senator Lambie said.
"If you want strong unions, a strong ALP, strong public support, he can't stay.
"If he takes the view that he'd rather live in a world where these laws are on the books than a world where his leadership is over, then that's a world we will wake up in."
Finance Minister Mathias Cormann denied the coalition was attacking the union movement.
"The government is focused on making sure all of the various organisations - whether they are employee or employer organisations - comply with the laws," Senator Cormann told Sky News.
"And where there is consistent and persistent breaking of the law, that the system is improved and that the opportunities to impose the rule of law are strengthened."