Formula One champion Red Bull scoffed at suggestions it manipulated Sunday's Brazilian Grand Prix to hand Mark Webber a first victory of the season.

Team boss Christian Horner said he was astonished that double world champion Sebastian Vettel finished the season-ending race, let alone in second place, after Red Bull advised him of a gearbox problem.

The fact Vettel set a number of fastest laps after allowing Webber to go past 30 laps into the 71-lap race aroused suspicions in the media room but Horner said there had been no deception.

"Of course there will always be people that have theories but categorically there was an issue," he said. "How on earth that gearbox got to the end of the race is beyond me. Thankfully it did and Mark ended up a deserving winner.

"If anybody thinks that was concocted in any way I can absolutely hand on heart guarantee you, based on the blood pressure that was on the pit wall ... it was a genuine issue," added Horner.

Webber had started second on the grid, alongside Vettel who had taken his record 15th pole of the season and was chasing a 12th win of the year. The Australian's last victory was in Hungary in August 2010 and Red Bull was eager for him to end the year as overall runner-up but his chances looked dim until the gearbox problem surfaced.

Vettel said he made clear to the team on the radio he could not keep the lead with the problem, or even be sure of finishing, and was willing to let Webber through to ensure the team still won the race.

The 24-year-old said he felt like the late Brazilian great Ayrton Senna, who famously won at Interlagos in 1991 with a McLaren whose gearbox failed progressively so that he ended up negotiating tight corners in sixth gear.

At the end of that race Senna had to be lifted from the car suffering from exhaustion and Vettel recognized the comparison was somewhat exaggerated.

Jenson Button of McLaren finished third to secure second place in the drivers' standings. Fernando Alonso of Ferrari was fourth and crowd favorite Felipe Massa, in his 100th race for Ferrari, was fifth. Adrian Sutil of Force India finished sixth and Nico Rosberg of Mercedes was seventh.

Lewis Hamilton also had a gearbox problem on his McLaren and eventually retired on lap 46.