Christian Horner has defended Sebastian Vettel, after Jacques Villeneuve slammed the reigning world champion for often behaving "like a child".

When comparing Vettel with his 2012 title rival Fernando Alonso, 1997 world champion Villeneuve last week admitted he was rooting for the Spaniard because he is cooler under fire.

When asked about the outspoken Villeneuve's likening of Vettel to "a child" when under pressure, Red Bull team boss Horner responded: "Honestly, I don't understand why Jacques said that."

The interviewer for Die Welt newspaper explained to Horner that Villeneuve was probably referring to Vettel calling Narain Karthikeyan an "idiot" this year, or when he thew his gloves after a car failure.

"Sebastian is an emotional person," Horner insisted, "and he wears his heart on his sleeve.

"It's normal that in such stressful situations, your feelings can sometimes win through.

"He wouldn't be human if he didn't."

Vettel's critics, however, say his meteoric success has said more about the German's equipment over the past years, often driving away with a clear road after dominating qualifying.

Indeed, Villeneuve said Vettel's mistakes as he climbed through the field from the back of the field in Abu Dhabi recently proved the point.

Horner countered: "I think he proved to the doubters (in Abu Dhabi) that he is a great racer. Sebastian did one of the best races I've ever seen."

And he warned that Vettel, on the cusp of his third consecutive title, 100th grand prix and aged just 25, is only getting better.

"Fernando is 31 years old and has probably reached his peak as an athlete. Sebastian, however, is far from it.

"He is still trying to develop as a driver and as a person," said Horner.