Before calling backmarker Narain Karthikeyan a "gherkin" and "idiot" in the wake of their collision, Sebastian Vettel was captured by his on-board camera twice displaying his middle-finger to the Indian driver.

"I think he's highly frustrated because he's having a tough season," Karthikeyan told the Deccan Chronicle on Wednesday.

"It's completely unprofessional to blame me for the incident. The derogatory remark only goes to show him in bad light.

"Just because he has a good car, he can't call others an idiot," Karthikeyan continued.

"I have won races in all the previous single-seater championships I have participated in so I don't need a certificate from Vettel."

Reports in Germany, including in the Kolner Express, Bild and Die Welt newspapers, claim that Red Bull driver's behaviour may have breached the new stricter code of conduct introduced by FIA president Jean Todt.

The FIA has been contacted for comment.

"He has breached the code of conduct," former F1 driver Marc Surer told Germany's Sky television. "You sign it when you get the license and then you have to behave correspondingly.

"Any behaviour that hurts other people or the sport is an offense," added the Swiss.

Asked what the penalties might be, Surer explained: "Anything from a warning to a license revocation. In this case I think it was quite understandable and there will be a mild punishment, if there is anything."

Hans-Joachim Stuck, however, is slightly less forgiving.

"When you're overtaking, misunderstandings can occur. I think Vettel needs to learn this.

"With him, the curve was always upwards and now it's not the case, and he needs to deal with that," the German legend told the DAPD news agency.

As for Vettel's description of Karthikeyan as a "gherkin", Stuck insisted: "It's better than 'asshole'."

Vettel's attack, however, was sustained, with Kleine Zeitung newspaper now quoting the Red Bull driver as having said: "Maybe formula one is not the place to learn how to drive."

Stuck responded: "If Sebastian had left more space, it would not have happened. It happens sometimes so it's a racing incident.

"He (Karthikeyan) didn't do it on purpose and it always takes two."

The HRT driver hit back by calling Vettel a "bully", and even David Coulthard - a Red Bull team consultant - defended Karthikeyan.

"He can't make his car invisible," the Scot is quoted as saying by the Mirror.

Also defending Karthikeyan was Force India driver Nico Hulkenberg, who told the Indian press this week: "From what I saw, it was not Narain's fault.

"So I don't really understand why he (Vettel) said all that."

Hukenberg's Force India teammate Paul di Resta added: "Narain is entitled to do as much on the track in comparison with someone like Vettel.

"Both are F1 drivers and are there to represent their teams."