Construction union boss John Setka is facing court action to stop him from stealing members from other sections of the powerful industrial body.
CFMMEU national secretary Michael O'Connor has lodged legal papers in the Federal Court in Melbourne seeking orders to prevent Mr Setka and 29 other construction division officials from poaching members from Mr O'Connor's manufacturing branch.
Mr O'Connor is seeking permanent orders stopping Mr Setka and other officials from "encouraging or advising any members of the union in the Victorian district of the manufacturing division of the union" to resign their membership of the division.
As well, Mr O'Connor wants orders preventing officers and organisers of Victorian-Tasmanian division from enrolling members who have resigned, and the members and their union dues to be returned to the manufacturing division.
No date has been set for a hearing.
It is the latest escalation of the war within the CFMMEU.
Mr Setka was forced out of the Labor party last year, having pleaded guilty to harassing his wife, but has controversially held onto his union position.
Last September, CFMMEU national and mining and energy division president Tony Maher received support for a motion condemning Mr Setka's "unprincipled actions" in stealing members from other divisions.
Mr Maher said at the time the union would not tolerate "breaches of rules and the principle of divisional autonomy".
The Morrison government has sought to use the CFMMEU ructions as an example of why "ensuring integrity" laws need to be passed.
The draft laws will go to the Senate when parliament resumes in Canberra on February 4.