A Queensland construction union official has been accused of threatening to “grab my bat and start swinging it around” if a senior project manager did not use union-preferred subcontractors on a state infrastructure project.

The building industry watchdog is seeking fines against Construction, Forestry, Maritime, Mining and Energy Union official Dean Rielly for the allegedly “improper” conduct on South Brisbane’s $45 million M1 freeway upgrade and has also accused him of refusing to follow safety protocols.