THE bystander was a mild-mannered academic from the University of Melbourne. Passing a building site on the Yarra's south bank, he witnessed a confrontation between a union official and a building manager. No punches were thrown but the two men pushed each other and grabbed at each other's shirts.

But agents of the federal building industry watchdog soon tracked the witness down and hauled him in for several hours of secret questioning, under powers that rival those of Australia's national security services.

The man cannot be named and cannot discuss the details of his interrogation for fear of imprisonment. Building unions say the innocent citizen's experience proves the Australian Building and Construction Commission is out of control, wielding powers greater than the police and equal to those of anti-terrorism bodies such as ASIO.

A spokeswoman for the commission confirmed it was the first time a bystander, not connected with a building company or a union, has been subjected to these powers. The legislation gives the commission the authority to question people - with or without a lawyer present - and overrides the right to silence. Witnesses cannot reveal the contents of the interview, even to their spouses, and risk up to six months in jail if they breach the law.

When contacted by the Herald, the witness declined to answer questions about his experience, saying only: "The laws governing