The 28-year-old signed a three-year deal with the Brackley based outfit in September 2012, leaving the McLaren team to whom he had been attached since the age of thirteen.
Hamilton has allowed his title charges to falter in recent seasons, leading to much speculation regarding his true commitment to the sport.
Speaking to Sporting Life, Stewart – a triple world champion – vented his concerns regarding Hamilton’s attitude and willingness to add to his 2008 crown.
The 73-year-old, now an ambassador of Lotus F1 Team, stated: “Personally, if I’d been Lewis, I wouldn’t have left McLaren.
“But as a 28-year-old, he should know what he is doing now.
“You just have to be damn careful you don’t get carried away with your own importance, your own celebrity, or your own schedule outside of being in the cockpit. It can be quite intoxicating.
“What Lewis needs to do is have more consistently good drives, never mind the mechanical issues, and he shouldn’t be distracted, something he should keep in the back of his mind.
“It’s about who you hang out with, what you do in your off time, how you are committing your off time towards your real time – and your real time is being a racing driver.”
However, Stewart believes that Mercedes team principal Ross Brawn will extract the most out of Hamilton, should the former Ferrari and Benetton technical director remain in his position at Brackley.
The former Tyrrell driver continued: “The Ross Brawn factor is important.
“He knows how to do it, and Lewis will have to work with him and depend on him, and Lewis, in time, will have to deliver.
“Ross has worked with drivers who have really delivered. He worked with [Michael] Schumacher from Benetton all the way through, and he knows how much Michael put in.
“Therefore he will think Lewis will have to put as much into that team, time-wise, commitment-wise, not just race-time wise, as Michael did.
“That’s going to be quite demanding, but there’s no reason why he shouldn’t go straight in and be competitive up front, not at all.”