Legal action is being taken against the Construction, Forestry, Mining and Energy Union (CFMEU) after it allegedly stopped workers accessing the building site of $80 million airport project.
Fair Work Building and Construction (FWBC) filed proceedings against the union and six officials on Thursday.
The federal agency alleges that on October 22, they arranged for about 100 people to block the site entrance to the Perth International Airport expansion project, disrupting 160 workers for four hours.
CFMEU assistant state secretary Joseph McDonald is also alleged to have verbally abused a female supervisor and her workers when they attempted to cross the picket line, calling her a "f***ing b**ch" and telling her colleagues they were "being pussy whipped".
The union' actions breached the Fair Work Act by seeking to coerce airport workers to comply with demands regarding unpaid worker entitlements, the agency said in a statement.
The FWBC investigated the underpayments, which were later paid.
"Unions should seek to exercise their lawful rights, rather than resort to using coercion and industrial tactics that hinder the construction of Australia's infrastructure," FWBC director Nigel Hadgkiss said.
The maximum penalties for such actions are $10,200 for an individual and $51,000 for the union.
The union declined to comment, given the pending legal action.