Prime Minister Scott Morrison has signalled he may try to ban the CFMEU.

Victorian secretary of the Construction, Forestry, Mining and Energy Union (CFMEU), John Setka, posted a picture on Twitter over the weekend of his children holding up a sign saying the Australian Building and Construction Commission (ABCC) should “go get fu#ked”.

“This is the straw that breaks the camel's back,” Mr Morrison told Melbourne radio station 3AW.

“I mean these guys are already demonstrating their lawlessness, and their thuggery, and their brutality, their threats. This goes on all the time, as we know.

“I'm looking very seriously at this.”

Mr Morrison said Jobs and Industrial Relations Minister Kelly O'Dwyer would investigate.

“John Setka is supposed to be the tough guy of the union movement, but uses his children to fight his fights,” Ms O'Dwyer said.

“It is beyond the pale. I am disgusted that any father would use his children in such an obscene way to attack a regulator for doing their job.

“The ABCC performs a critical role in stopping thuggery, intimidation and corrupt behaviour on our construction sites and they deserve our support and thanks.”

The ABCC has reportedly offered to meet with Mr Setka.

The Royal Commission into Trade Union Governance and Corruption investigated the process of having the union's registration cancelled, but did not make a recommendation to do so.

The final report from the royal commission argued individual union officials were responsible for misconduct.

“Any targeted action to combat the culture of the CFMEU should focus on the officials of the union,” the report stated.

Mr Setka has since deleted the message, saying; "Was emotional on Father’s Day after tough year on family. Shouldn’t have included kids. Now deleted."