Haas, the new American team, has stepped up the tone of its rhetoric amid criticism of its close alliance with Ferrari.

The team's two points finishes in Australia and Bahrain respectively have sparked controversy in the pitlane that driver Romain Grosjean brands "jealousy".

Technical boss Gunther Steiner, meanwhile, said that Haas is doing nothing wrong by buying parts from Ferrari, declaring in Shanghai: "While people can express their views, I suggest everyone also reads the rules, as they are easily available."

Now team founder Gene Haas has come out with an even stronger rejoinder to the critics, telling reporters in China that the complaining is simply "sour grapes".

"A lot of the teams at the back really don't know what competition is," he said. "They're getting maybe a little too fat and happy.

"I guess there are a lot of whiners in F1 that talk about our success."

Haas's final comment about "whiners" may also be a reference to F1 supremo Bernie Ecclestone, who told business journalist Christian Sylt recently that the new American squad's car is good "because it's a Ferrari".

The French news agency AFP said that Haas, 63, was even ready with a "sheet of paper detailing a list of parts his team makes itself".

An insider told GMM F1 that the Californian is being very bold in facing down Ecclestone.

"I've honestly never seen anything like that before and it made me think that success has gone to his head," the source said.

The source explained that the fact Haas has compiled a written list of the parts it makes for itself could be a sign he is "worried" about a potential challenge.

"We never came into this [sport] to run at the back," Haas insisted. "If people don't like that then that's their problem, not my problem."

The season continues tomorrow with the Chinese Grand Prix.