Jenson Button remains on track for a maiden world championship after the FIA today ruled his Brawn GP car is legal.

The governing body's International Court of Appeal confirmed the Briton as the winner of the Australian and Malaysian Grands Prix after dismissing a protest against the diffusers on the Brawn GP, Toyota and Williams cars.

The ruling will anger rivals of the diffuser three' who must now spend millions redesigning their own cars around new diffusers if they are to be competitive.

But team owner Ross Brawn is delighted that what he called an “innovative approach” to the regulations had been vindicated by the Paris hearing.

Ahead of Sunday's Chinese Grand Prix in Shanghai, where Button will start clear favourite to win, Brawn said: “We respect the right of our competitors to query any design or concept used on our cars through the channels available to them.

“The FIA technical department, the stewards at the Australian and Malaysian Grands Prix and now five judges at the appeal have confirmed our belief that our cars have always strictly complied with the technical regulations.”

Brawn (below) added: “The decision brings this matter to a conclusion and we look forward to continuing on the track the challenge of what has been a very exciting start to the season.”

Opposition to the diffuser three' had been led by Ferrari, Renault, Red Bull and BMW-Sauber.

They claimed that the two-tier design of the diffusers — a vital part of the aerodynamics which disperse air from beneath the rear of the car — offered an unfair advantage.

But the FIA said: “Based on the arguments heard and evidence before it, the court has concluded that the stewards were correct to find that the cars comply with the regulations.”

A full verdict is expected to be published over the weekend. There is no further course of action open to the protesters, who now face a race against time to make their cars capable of challenging for this season's title.

Ferrari team principal Stefano Domenicali said: “Unfortunately this decision forces us to intervene on fundamental areas of the car's design in order to be able to compete on an equal footing with some of the teams from a point of view of the technical regulations, and that will take time and money.

“We will now double our efforts to get the team back to the highest level of competitiveness.”
Renault had already been working on a new diffuser, which their drivers Fernando Alonso and Nelson Piquet are expected to use in China.

Button will go into the race with a five-point lead over team-mate Rubens Barrichello, while Toyota's Jarno Trulli is third.