Lewis Hamilton has issued another warning to his employer McLaren-Mercedes that should the team not pick up its form sharpish, his 'patience will be seriously tested' - reasoning that unlike Rubens Barrichello, he is far from 'content with being in F1 and just existing'.

For the third campaign in succession, 2008 F1 World Champion Hamilton has not genuinely had a shot at the drivers' crown in 2011, as McLaren has struggled to keep pace with Red Bull Racing and - on occasion - Ferrari. That prompted sustained criticism earlier this season, followed by speculation linking the British star to a future switch to the Milton Keynes-based squad himself - but of late, he seemed to have settled down at Woking again and set his sights on the long game. Until now.

"In terms of my career, I have at least another five to ten years," he reflected, according to The Sun. "At some stage, if it continues the way this is going - which I don't think it will - then patience will be seriously tested.

"Seb [Vettel] will come back just as confident as he has been this year [in 2012], so we have to raise our game. We had a big technical review meeting recently, and I am pushing. No-one asked questions except for me. I was like, 'sorry, I have some questions...'

"There are some drivers that are content with being in F1 and just existing. Maybe they have families. Look at Rubens Barrichello - he seems content with where he is. Then there are people like me who only exist to be the best. If you aren't busy trying to be the best, then you're not busy doing anything."

The undertone is clear - that unless McLaren are able to finally come out-of-the-blocks fighting right from the 'off' in 2012, then he might be 'off' himself - but the contrast with Barrichello is sure to stir up controversy.

The Brazilian might be one of the sport's journeymen, but he has also been a hugely successful one, as an eleven-time grand prix-winner and twice runner-up in the title standings. As he bids to extend his career into an incredible 20th season in 2012 by remaining with Williams, however, the 39-year-old was quick to play down the comment.

'About Lewis Hamilton, some said there was an interview where he said bad things about me,' he tweeted. 'I talked to him and he said they were not true; for me, this is more than enough. After so many years, I got used to people inventing things just for the sake of inventing...'

As to his more reserved performance in the Italian Grand Prix at Monza last time out, meanwhile - both on the track and also through his refusal to criticise Michael Schumacher's driving afterwards - Hamilton has told the official F1 website that 'I wasn't downbeat, but I didn't go balls out, basically...I didn't take too many risks; it was all about finishing the race and walking away with some dignity'.

And what did his McLaren team principal Martin Whitmarsh make of that?

"I told him that was a very disciplined drive," the Englishman reflected, "but I would like the old Lewis back."