Pole-sitter Vettel was passed by the Red Bull of Max Verstappen round the outside of the first corner on the opening lap, and was forced wide in the battle – which allowed Hamilton through as well.

But Vettel clipped Hamilton's right-rear on the exit of Turn 3, damaging his own front wing and giving the Briton a puncture.

After both pitted early, Vettel fought through the pack to finish fourth, while Hamilton brought the car home in ninth for his worst finish of the year - which was still enough to make him 2017 champion with two races to spare.

Asked about the "unusual" way in which Hamilton won the title, Lauda told Sky Sports: "Unusual? When you're world champion, you're world champion, it's very simple. Nobody cares how you do it.

"What I don't understand is the aggressive manoeuvre of Vettel in the first corner, which hit Lewis hard. It was not his fault at all.

"And then his drama started. But in the end it worked out fantastically."

Speaking post-race, Hamilton said he believed he had given Vettel enough room for the pair to avoid contact.

"I had a good start. I don't really know what happened at Turn 3 - but I gave him plenty of room."

Lauda praised Hamilton, who overturned a mid-season deficit to Vettel with a run of five wins in six races before clinching his fourth F1 title in Mexico, for getting the most out of a "difficult" Mercedes W08 this year.

"Lewis was especially this year able to improve a lot," said Lauda, himself a three-time world champion.

"If you want to be a four-time world champion, you have to always get better and better and better. From last year to this year, he got much better.

"It's an incredible step forward. It's a difficult car to drive, not so quick as last year, not so easy, and he really made it because of his own performance."

Additional reporting by Jonathan Noble