A Brisbane City Council bus driver is fighting an assault charge after allegedly punching a cyclist in the face after he was called "fat and stupid" during a peak-hour row in Brisbane's inner-city two years ago.

Leon James Zahnow, 36, pleaded not guilty in Brisbane District Court today to one charge of assault occasioning bodily harm, following the road rage incident.

Crown prosecutor David Finch told the court Mr Zahnow pushed and punched 57-year-old cyclist Gregory Ralph Jardine on Given Terrace in Paddington about 7.30am on December 10, 2009.

Mr Finch said the pair became involved in a "heated argument" after the bus nearly collided with the cyclist on Caxton Street near the Iceworks Restaurant Bar and Lounge.

The jury was told Mr Jardine, an architect on a morning bike ride, "interfered" with the side mirror of the bus and the windscreen wipers, before banging repeatedly on the front door of the bus once it stopped several metres away on Given Terrace.