Somerset's Jenson Button is free to race on in the Brawn GP car with which he has won maximum points this season with two Grand Prix victories.

The FIA International Court of Appeal have today ruled that the design of the Brawn, Toyota and Williams cars is legal and “complies with the applicable regulations”.

During an eight-hour hearing yesterday Ferrari, Renault, Red Bull and BMW Sauber challenged the three teams in front of five ICA judges, attempting to overturn the FIA’s initial ruling that the design of the diffuser used by Brawn, Toyota and Williams was legal.

However, a statement this morning read: “The FIA International Court of Appeal have decided to deny the appeals submitted against decisions numbered 16 to 24 taken by the Panel of the Stewards on March 26 at the Australian Grand Prix and counting towards the 2009 FIA Formula One World Championship.

“Based on the arguments heard and evidence before it, the court concluded that the stewards were correct to find that the cars in question comply with the applicable regulations.

“Full reasons for this decision will be provided in due course.”

The ruling means the teams keep the points they have won in the two races so far this season with Brawn GP's Button leading the drivers' standings after two victories.

At the centre of yesterday’s debate aired in front of five judges, and with a remarkable 38 other personnel present – either legal counsel, team or FIA representatives – was the legality of the diffuser currently used by Brawn GP, Toyota and Williams.

The device has helped Button win the opening two grands prix of the season in Australia and Malaysia, and with Brawn GP heading the constructors’ ahead of Toyota.

Although Ferrari, Renault, Red Bull and BMW Sauber argued fervently against the design, the judges have sided with the FIA and the stewards who had already determined the part was legal.

That has left Brawn GP, along with Toyota and Williams, free to race in this weekend’s Chinese Grand Prix in Shanghai, and forced their seven rivals into playing catch up.

A Toyota statement read: "As we have maintained throughout, our team studied the wording of the new 2009 regulations in precise detail to ensure we interpreted them correctly.

“We also made full use of the consultation procedure with the FIA which was a helpful process to ensure our interpretation of the technical regulations was correct.

“Therefore we had every confidence that the design of our car would be confirmed as legal, firstly by race stewards in Australia and Malaysia and subsequently by the Court of Appeal.”

Chairman and team principal Tadashi Yamashina added: “I was confident the Court of Appeal would reach this verdict and I am satisfied with it.

“This has been a challenging period for Formula One and I am pleased this issue is now in the past and we can focus on an exciting season on the track.”