Renault and Ferrari have made clear their concerns about rear diffusers, but McLaren has not followed suit in the same fashion.

Renault and Ferrari have made clear their concerns about rear diffusers, but McLaren has not followed suit in the same fashion.

It is believed that the respective diffuser designs on the Brawn, Toyota and Williams cars are controversial according to the spirit of the 2009 rules, but technically legal when exercising a loophole in the wording.

Renault's Flavio Briatore has accused "three teams" of producing illegal cars, while Ferrari team boss Stefano Domenicali recently admitted that some designers "took a different approach" with the rules.

When the controversy arose, FIA president Max Mosley said the teams involved had been "clever" in their application of the regulations but could not rule out a formal protest at scrutineering in Melbourne.

"We accept the rule interpretation of the FIA," Norbert Haug, Mercedes' competition chief in collaboration with McLaren, told Express.

"Therefore the solutions seen so far are legal," he added.

It is understood that Brawn's diffuser design with its BGP001 car has taken the Williams and Toyota concept to a new level.

However, it would be simplistic to boil down the team's performance to one element, especially as many paddock figures have spoken with high praise about the Mercedes-powered car's total aerodynamic package.

Team head Ross Brawn, likened to Albert Einstein in a caricature by the German newspaper Bild, said: "It will take the other teams some time to copy our ideas, if they manage to at all."