Max Verstappen says it is "bullshit" to suggest Formula 1 cars are not challenging enough, and is baffled by Romain Grosjean's claim that driving a kart is harder.
Lewis Hamilton has suggested this season that the current generation of Formula 1 car is too easy to drive, while Grosjean revealed he was more tired driving a few laps in a kart than he feels during grands prix.
But their comments have not impressed Verstappen, who said F1 cars remain a challenge to drive and suggested Hamilton only holds his view because his Mercedes is so good.
"That's bullshit to me," said Verstappen, when it was put to him that F1 is not challenging enough currently.
"We are now so much faster than we've been in previous years. I don't understand where this is coming from."
Asked about Hamilton's claim that he could easily do three races in a row, Verstappen said: "If you have such a good car, you can drive at 90%."
Verstappen said he also was confused about why Grosjean made so much of finding a kart hard to drive.
"What Grosjean said, I don't understand at all," explained the Red Bull driver. "With karting you use very different muscle groups.
"If I would go karting now, after 20 or 30 laps I would also be completely messed up. While when I was 15, I could drive 300 laps in one day and had no problems at all.
"Does that mean that I am not as strong as when I was 15? No, not at all. You just use very different muscles. You ask a lot more from your forearms.
"It makes no sense at all to make that comparison.
"If you would put mates of mine who are still karting in a racing car, they wouldn't feel their necks the next day, while they drive 300,000 laps a year in a kart. So I think this is a very strange comparison."