The aircraft was using a taxiway which had a row of cones positioned about 11.5 m from the centre-line to indicate a step in the sealed surface. The pilot saw a fuel tanker parked some distance away from the cones, but, assuming that the cones were taxiway clearance markers,continued to taxy along the centre-line. The port wing struck the top of the tanker about 15 m from the aircraft centre-line and about two metres from the wing tip. There were works in progress in the area of the occurrence. Tanker drivers were required to park their vehicles not closer than 24 m to the centre-line of the taxiway, but there was no visual delineation of this distance.