Ross Brawn is confident the 'diffuser gang' will win their day in court on Tuesday as Formula One steels itself for this year's first major off-track showdown.

Ferrari, Renault, BMW Sauber and Red Bull face Brawn GP, Williams and Toyota at an International Court of Appeal hearing in Paris many feel could determine the destiny of this year's championships. At the heart of the matter is the conceptual design of the diffuser used by the latter three which Ferrari, Renault, BMW Sauber and Red Bull believe should be deemed illegal.

The FIA and the stewards in Australia and Malaysia, where Brawn GP driver Jenson Button claimed two victories, have already deemed the part is legal and Brawn is convinced the judges will ultimately agree, saying: "The stewards have said it is legal. It's the International Court of Appeal that is going to hear whether the stewards have made an incorrect decision."

He added: "Some teams are unhappy with that decision, but it (the diffuser on his team's cars) is in line with our understanding.

"You have to see how these things go, but even if they decide there is a different interpretation, I don't think they'll wipe out what went before because we've been told our car is legal."

If the court sides in favour of Ferrari, Renault, BMW Sauber and Red Bull, they have it in their power to overturn the results of the two previous races.

Brawn GP, Toyota and Williams would also quickly have to re-design that part of the car to fall in line with the others, with the next race in China a few days away.

If they agree with the 'diffuser three' it would force the seven remaining teams into playing catch up because as has been witnessed there is a clear performance difference.

One of the main complaints centres around cost because if Ferrari et al do lose, they will be forced into a radical re-design of their cars as the diffuser affects a number of areas.

"I think some teams will be able to do it very quickly, but for other teams it will be more difficult because of their suspension configuration or other elements of the car," added Brawn.