Denny Hamlin has been fined $25,000 by NASCAR for criticising the quality of racing with the new Gen-6 car over the opening two events.
The Joe Gibbs Racing driver was issued with the penalty after NASCAR determined that the remarks he made in pit road after last weekend's Phoenix race were in breach of section 12-1 of the series rule book, which covers actions detrimental to stock car racing.
A statement claimed Hamlin's comments had gone beyond the boundaries of what NASCAR considered acceptable.
"Following the NASCAR Sprint Cup Series event last Sunday at Phoenix International Raceway, Denny Hamlin made some disparaging remarks about the on-track racing that had taken place that afternoon," it said.
"While NASCAR gives its competitors ample leeway in voicing their opinions when it comes to a wide range of aspects about the sport, the sanctioning body will not tolerate publicly made comments by its drivers that denigrate the racing product."
Hamlin finished third at Phoenix after starting at the rear of the field, but said that his progress through the pack was due to strategy and other drivers making mistakes rather than by overtaking.
"I don't want to be the pessimist, but it did not race as good as our generation five cars," he said.
"This is more like what the generation five was at the beginning. The teams hadn't figured out how to get the aero balance right.
"Right now, you just run single-file and you cannot get around the guy in front of you. You would have placed me in 20th place with 30 [laps] to go. I would have stayed there - I wouldn't have moved up. It's just one of those things where track position is everything."
Hamlin told Fox Sports on Thursday that he will not pay the fine.
"This is the most upset and angry I've been about anything in a really, really long time [about] anything that relates to NASCAR," he said. "The truth is what the truth is and I don't believe in this, I'm never going to believe in it.
"As far as I'm concerned, I'm not going to pay the fine. If they suspend me, they suspend me. I don't care at this point."
Other drivers have been spoken about the difficulty of overtaking with the new cars, although Hamlin is the only one to have been punished.
Mark Glendenning, US editor
Hamlin should expect plenty of sympathisers in the Las Vegas paddock this weekend.
In coming down so hard on what frankly seem to be innocuous comments, NASCAR's efforts to protect its image put it at risk of doing exactly the opposite: its response seems overblown and paranoid.
If Hamlin was speaking during pre-season testing, you might understand the series being concerned. As it stands, he hasn't said anything that fans and viewers couldn't see for themselves.
Yes, the car is in an early stage of development, and improvements will be made. But so far, the racing has been underwhelming.
Fining Hamlin won't change that.