Red Bull design guru Adrian Newey has questioned the safety of the F-duct system, the controversial device introduced by McLaren, subsequently used by Sauber and now looking to be taken up by more teams including Ferrari.

The system sees the driver close a vent in his cockpit - in McLaren's case worked by the left knee - which stops the airflow through a slot that runs along the top of the engine cover, effectively stalling the wing and giving the driver as much as 6 kph more on the straights.

However, Newey, whose 2010 creation is the subject of much speculation since it is widely thought to be the class of the field, is concerned at the safety aspect of the F-duct.

"McLaren's F-duct is intelligent and opens new ways," he told Gazzetta dello Sport. "However I'm worried about the safety aspect. Many cars, including ours, have been re-designed around the double diffuser. The rhythm of development is high and the speed at which you bring new things remains fundamental. We are looking at the F-duct. We have understood how it works, but to get it to work properly is another thing. We don't know when we can take it to the track.

"The difficult thing is that McLaren has designed the chassis around that system," he continued, but the rules prevent you from modifying the chassis. Every new thing has to be included in the current structure."