Jenson Button has accused Flavio Briatore of being "bitter" after the Renault boss suggested Brawn GP's current dominance is damaging the credibility of Formula One.

Button has reaped the benefits of the controversial double diffuser on his Brawn car and Briatore said in an interview with La Gazzetta dello Sport: "Our (McLaren, Ferrari and Renault) drivers are or have been world champions. Then you have a (Brawn GP) driver who was almost retired, and another who is a 'paracarro' (an Italian term for a concrete roadside post), fighting for the championship."

But Button, who on Friday topped the timesheets in second free practice, said: "It is very unfair for Flavio to comment as he has just because he is very bitter."

The FIA's International Court of Appeal on Wednesday ruled the diffuser used by Brawn, Toyota and Williams as legal, leaving the other teams scrambling to make the necessary technical changes and catch up.

The 29-year-old added: "He is obviously a very angry man after the diffuser issues and is very disappointed they have not produced a car that is as competitive as ours.

"We have produced as competitive a car because of the workforce back in Brackley and you cannot take that away from them.

"It is unfair to say that as they have worked very, very hard in difficult circumstances."