An employee of Australia's hardware giant Bunnings who allegedly threatened to shoot everyone in the store while impersonating cowboy actor John Wayne has lost his unfair dismissal claim.

Bunnings has also banned the former Cairns employee from all its stores in Australia and police have suspended his weapons licence.

Australia's national workplace relations tribunal Fair Work Australia heard the man would visit the desk of the store's female customer service manager six to seven times before lunch each day, and witnesses overheard him making threats through John Wayne impersonations.