Prime Minister Scott Morrison has thrown his support behind independent senator Jacqui Lambie after construction union boss John Setka was reported as launching a foul-mouthed rant against her.
Senator Lambie labelled Mr Setka a "meathead" this week and called on him to resign or she would back the federal government's "Ensuring Integrity" bill aimed at deregistering rogue unions.
Nine newspapers reported comments recorded at a meeting of union activists on Thursday, the first since the Tasmanian senator expressed her views.
"In the end who the f--- is a politician to tell a union secretary or any union official who the f-- is going to run the joint or not? When the f--- is that happening?" Mr Setka is reported as saying.
Mr Morrison said the sort of abuse Senator Lambie has copped is "absolutely unacceptable".
"She's found a way back into the parliament. She deserves respect, not the sort of abuse that we've seen levelled at her, particularly for being prepared to consider voting for the bill," the prime minister told reporters in Launceston, Tasmania on Saturday.
"Just by being prepared to consider voting for it she's being subject to all this bullying of her. But you know, I reckon Jacqui's made of tougher stuff than that. I reckon Jacqui can deal with that."