The CFMEU has vowed to fight any attempts to deregister it after Prime Minister Scott Morrison revealed he is weighing up banning the union.

Mr Morrison has called on Labor to sever ties with the construction union after a prominent official used his children to campaign against the building industry watchdog.

CFMEU Victorian state secretary John Setka posted a picture of his children holding a sign saying 'Go get f*#*ed' with the caption "Leave our dads alone and go catch the real criminals you cowards".

Industrial Relations Minister Kelly O'Dwyer on Monday said the government will "consider all options available to it" to deal with the CFMEU.

The union's national construction secretary Dave Noonan said he was not surprised the government had resurrected the CFMEU "bogeyman" to scare voters.

"When the Liberal Party is focused on good old-fashioned union-bashing, you know they're in trouble," Mr Noonan said.

"Any attempt to deregister the union will be vigorously resisted."

Earlier, the prime minister said Mr Setka's behaviour made his skin crawl.

"The CFMEU has behaved under John Setka like a bunch of thugs and to involve his children in that, I think, is one of the ugliest things I've seen," Mr Morrison told Sydney's 2GB radio.

Mr Setka has since deleted the tweet.

"Mea Culpa. Was emotional on Father's Day after tough year on family. Shouldn't have included kids. Now deleted," he posted on Twitter.

Mr Morrison wants Mr Shorten to cut ties between the Labor Party, Mr Setka and the CFMEU.

"Bill Shorten's got his arms all around John Setka, and John Setka's got his arms all around Bill Shorten," he said.

But Mr Shorten, who said the post was wrong, urged the prime minister to spend as much time worrying about energy prices as union officials' tweets.

"Let's call it as it is - Mr Morrison has leapt on the tweet like a drowning man will sort of grab at a fig leaf," the Labor leader told reporters in Brisbane.

Mr Morrison said he would "of course" consider deregistering the union and discuss it with Ms O'Dwyer.

"This is the straw that breaks the camel's back," he told Melbourne radio 3AW.

"I'm looking very seriously at this."

Master Builders chief executive Denita Wawn was lukewarm on the prospect of banning the union outright.

"Deregistration of the entire union ... would impact on those divisions actually doing the right thing," Ms Wawn told Sky News.

Instead, she wants the parliament to pass legislation allowing the construction division to be deregistered.