John Setka and another CFMEU leader, Shaun Reardon, have launched legal action against executives of the construction supply company Boral over blackmail charges that were dropped earlier this year.
In documents lodged with the Supreme Court, the construction union bosses are seeking damages from Boral executives Paul Dalton and Peter Head.
In 2015, Mr Setka — who is the secretary of the CFMEU in Victoria — and Mr Reardon — his assistant — were arrested and charged with blackmail.
It followed claims by the Boral executives that the company had been threatened with union action if it continued to supply concrete to Melbourne building sites operated by Grocon.
The CFMEU was waging an industrial campaign against Grocon at the time, based on concerns about worksite safety and access by union officials to Grocon worksites.
The allegations centred on a meeting between the four men at a cafe in North Melbourne in April 2013.
"Setka and Reardon did not threaten either Dalton or Head and did not otherwise make any unwarranted demand with menaces" during that meeting, the document states.
Prosecutors abandoned the charges in May.
The court documents alleged Mr Dalton and Mr Head "provided false information to police and withheld relevant information from the police".
"Dalton and Head, in initiating and maintaining the criminal proceedings, acted maliciously," the statement of claim lodged on Tuesday said.
A spokesman for the union said it is acting on what it calls an "outrageous abuse of law".
Boral told the ABC it has not received any proceedings, but said it was "confident that Boral and our executives have always acted with the utmost integrity and honesty in this case and will continue to do so".
