Denny Hamlin is refusing to pay a fine of $25,000 assessed to him by NASCAR for making derogatory comments about the new Sprint Cup Series race car, the Gen-6, last weekend at Phoenix International Raceway.

NASCAR handed down the fine to Hamlin on Thursday after officials determined that he violated Section 12-1 (actions detrimental to stock car racing) of the 2013 NASCAR Rule Book. Hamlin did not receive a loss of points, and he was not placed on probation.

This past Sunday at Phoenix, Hamlin finished third in the Subway Fresh Fit 500 after starting from the rear of the field due to an engine change. He was asked what his thoughts were of the Gen-6 following the second race of the season.

His response, "We learned a lot. I don't want to be the pessimist, but it did not race as good as our generation five cars. 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. If 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."

NASCAR issued a statement when it announced Hamlin's penalty.

"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," the statement read. "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 was furious when he learned of his penalty and said he was not going to pay the fine.

"Ultimately,"I'm not okay with it," Hamlin said on Thursday at Las Vegas Motor Speedway, where Sprint Cup teams spent the day testing the car in preparation for Sunday's 400-mile race here. "This is the most upset and angry I've been in a really, really long time about anything that relates to NASCAR ... As far as I'm concerned, I'm not going to pay the fine. If they suspend me, then they suspend me. I don't care at this point."

According to NASCAR rules, Hamlin could be suspended from competition if he does not pay the fine in a timely manner.

Hamlin noted that NASCAR was upset with him in comparing the Gen-6 with the previous race car, the fifth generation car, which was commonly referred to as the Car of Tomorrow when it made its debut in 2007. NASCAR used that vehicle for five years. Hamlin said he was giving his opinion about the Gen-6, and he didn't think it was a bad opinion.

"I have to be careful, because I don't want to make things worse than they already are, and this is something that was absolutely nothing and it got blown into something," he said. "It's just going to be worse for them, so let them deal with it."

Hamlin also vowed not to make any more comments that relate to competition.

"To be honest, I'm not going to say anything for the rest of the year, as long as it relates to competition," he said. "You can ask me how my daughter is, talk to me after wins about what have you, but as long as it relates to competition, I'm out from here on out."

Drivers and teams have learned that the Gen-6 cars -- Chevrolet SS, Ford Fusion and Toyota Camry -- are faster and have more downforce and better grip than the last cars. But drivers have noticed that passing is difficult, and there has been a lack of side-by-side racing.

During a press conference held at the 1.5-mile Las Vegas racetrack, NASCAR vice president of competition Robin Pemberton defended the sanctioning body's decision to penalize Hamlin.

"We give them (drivers) quite a bit of latitude, but you can't slam your racing, you can't slam your product," Pemberton said. "That's where it crosses a line."

Hamlin can appeal the penalty. Pemberton pointed out that Hamlin would have to notify NASCAR in writing of his appeal.

"It's like every other appeal," he said. "Over the course of time, you remember mechanics and crew chiefs, whatever, if they appeal, then they can continue to carry on business as usual until the appeal has been heard and ruled on."

On Thursday night, Hamlin posted on his Twitter account that he will appeal. He continued to voice his opinion on the fine as well.

"The short of the long of it is I believe I was severely disrespected by NASCAR by getting fined," he tweeted. "I believe that the simple fact of us not even having a conversation about this issue before I was hit with a fine has something to say about our relationship.

"What I said was 1 sentence taken completely out of context. Most drivers will tell you that we constantly have our AND nascars best interest in mind when speaking. On the other hand I am a person that worked very hard from the BOTTOM to get where I am today and someone telling me that I can give my 100 percent honest opinion really bothers me.

"Since being fined in 2010 I have been a lot more careful about what I say to media and I felt this past weekend felt completely in my rights to give a assessment of the question asked. I feel as if today NASCAR lost one of its biggest supporters vocally of where our sport is headed. So in the end there are no winners.

"I said today I would not pay the fine. I stand by that and will go through the process of appealing. Trust me, this is not about the money.. It's much deeper. I will now shift my focus on giving FedEx and my team what they deserve this weekend, a win."