Lewis Hamilton's bid to become the first rookie driver to win the Formula One world championship is firmly back on track after he was cleared of any wrongdoing in the accident involving Mark Webber and Sebastian Vettel in Japan.

But the 22-year-old has revealed he is becoming disillusioned and hinted he could walk away from the sport if distractions off the circuit continue to overshadow his achievements on it.

He said the incidents away from the track were "a shame for the sport" and if they continue "it's probably not somewhere I really want to be".

The FIA confirmed on Thursday that the McLaren star was under investigation for erratic driving behind the safety car as new footage had come to light regarding the incident on lap 45 of the 67-lap race.

The new footage was a video said to have been recorded by a fan in the grandstand at the Fuji Speedway and posted on YouTube.

It appeared to show Hamilton veering off to the right of the track and braking excessively in the last part of the circuit, in turn causing Webber to slow down and Vettel to run into the back of the Australian's Red Bull.

It was brought to the attention of the stewards by Vettel's team Toro Rosso in a bid to have the German's ten-place starting grid penalty for tomorrow's Chinese Grand Prix thrown out.

However, it led to closer scrutiny by the authorities of Hamilton's behaviour behind the safety car in what were appalling conditions.

If found guilty Hamilton was, at the very least, likely to have been hit with the same penalty as Vettel but could also have had the ten championship points he picked up after taking the chequered flag at Fuji in impressive style annulled.

But after a meeting involving all three drivers and representatives from each team yesterday, it was decided no further action was to be taken against the Briton, while Vettel also had his penalty reduced. Webber was particularly critical of Hamilton's driving during the two safety car periods at Fuji, accusing him of braking and accelerating excessively as he led the field around in poor visibility.

"I think he did a poor job behind the safety car," Webber had said.

"He did a poor job and that's it. He spoke in the driver's briefing about how good a job he was going to do and he did the opposite. But we know for next time.

"It definitely contributed to Sebastian hitting me up the back. We were confused what the other car was doing because it wasn't doing what it was supposed to do, clearly."

But Hamilton will warmly welcome the stewards' decision after he had earlier hinted he could walk away from Formula One if politics continued to overshadow his performances.

"It's just a shame for the sport and if this is the way it's going to keep going then it's probably not somewhere I really want to be,'' he said.

"Formula One is supposed to be about hard competition, fair and that's what I've tried to do this year, just be fair.

"If I've been in the wrong, I've been the first to put my hand up, or apologise at least, and I don't mind being given a penalty but there's been some real strange situations this year where I'm made to look the bad person or, by the looks of it, this weekend could be given a penalty.

"I had a good weekend, I don't think I put a foot wrong and I didn't do anything to harm anyone else or put anyone else in danger but I've come away to China and no doubt I'm going to be punished for something.

"I just think it's a real shame for the sport."

Hamilton holds a 12-point lead over closest challenger Fernando Alonso and will also become the youngest driver to win the world championship if he drops no more than one point to Alonso in tomorrow's race, which is expected to again take place in wet conditions because of a typhoon hovering menacingly off the coast of China.

But he was only fourth quickest in both of yesterday's practice sessions.