Red Bull team principal Christian Horner has admitted that he was lost for words to describe Sebastian Vettel after he secured a fourth consecutive world title with victory at the Indian Grand Prix.

The German led from start to finish at the Buddh international circuit to claim a sixth straight race win and, in the process, crown Red Bull constructors' champions.

Horner told reporters: "It is an amazing day, words fail me for what Seb has done for the last four years. It is gutting on the day we win the constructor's championship that Mark Webber didn't finish and make it one-two.

"There were huge concerns [about the electrics] so we were switching things off, first the Kers and we even stopped him using his drinking bottle because we didn't know what the problem was but it didn't stop him."

Vettel's triumph means that only Juan Manuel Fargio [five] and Michael Schumacher [seven] have won more Formula 1 titles.