A Federal Court judge has lashed the CFMEU administration for resisting an investigation into the union’s alleged boycotting of an Indigenous firm from a Victorian government site, which included alleged threats to rip the owner’s head off.

For five months, the construction union has been fighting the Fair Work Ombudsman’s directions to give up documents involving the CFMEU stopping labour hire firm Marda Dandhi from working on commercial sites and the Victorian government’s $760 million Monash Freeway upgrade.