Lando Norris said the decision to penalise him for a passing move on title rival Max Verstappen in the United States Grand Prix was a "momentum killer" for his championship hopes.
The penalty, which the McLaren driver described as "rash", demoted Norris from from third to fourth place, one position behind Verstappen, who has now extended his championship lead to 57 points with five races to go and 146 points still available.
Norris also said he had "driven like a muppet" at the first corner, and allowed Verstappen to get up his inside and force him wide, a move that cost both of them places to eventual race winner Charles Leclerc of Ferrari.
Both incidents were controversial, but Norris and his McLaren team were more concerned by the defining moment of the Austin race with four laps to go.
Norris had spent most of the race behind Verstappen, but an offset strategy gave him a tyre advantage in the second stint and he closed on to the back of the Red Bull with 12 laps to go.
The two rivals spent the next eight laps battling, sometimes running side by side, until Norris tried to capitalise on the best opportunity he got.
He went for the outside line at Turn 12 as Verstappen defended the inside. Both cars ran off track on the exit and Norris emerged in front.
Verstappen immediately complained that Norris had overtaken him off the track, which is not allowed. Norris and McLaren saw the incident the other way around.
Norris said: "For me, the thing that is incorrect is what Max did, which is defend his position by going off the track and effectively keeping his position. He over-defended and made a mistake and gained from that.
"I had to go off the track. It is impossible for people to know whether I could have made it on the track or couldn't, therefore you cannot steward that kind of thing."
Norris and McLaren team boss Andrea Stella said the stewards should have reviewed the incident with both drivers after the race.
"For me it's just a rash decision," Norris said. "They don’t hear or understand our points, which they should do after the race. They just want to make a decision at the time so they don’t alter points and podiums and things like that.
"But they don’t hear my point or my team's point or Max's point, which I don’t think is the most correct thing. But today it's a penalty and there's not a lot I can do apart from accept that.
"It was a great battle. Max defended very well but he ended up on top and congrats to him."
Norris said the stewards were "just guessing and I don’t think that’s how stewarding should be done".
Stella drew comparisons with other incidents in which Verstappen has driven in the same way during his career.
"The defending car goes just straight at the apex," Stella said. "We checked the video multiple times; it is just going straight. It is just going off the track as much as Lando is doing, just giving no chance for Lando to compete the manoeuvre.
"If I was a journalist, I would have done a bit of statistics how many times Max has used this way for defending. Both cars go off track. So I think both cars are gaining an advantage if there is an advantage gained. So I think it was at least neutral."
Verstappen rejected Stella's remarks, saying: "They complain about a lot lately anyway, but it's very clear in the rules. Outside the white line, you cannot pass. I've been done for it as well in the past."
The stewards' report said that Norris was not level with Verstappen at the apex of the corner, so Norris had "lost the right to the corner".
It added: "As (Norris) left the track and returned in front of (Verstappen), it is deemed to be a case of leaving the track and gaining a lasting advantage."
They added that the standard penalty was 10 seconds but this was reduced because of Verstappen’s driving: "Having committed to the overtaking move on the outside, (Norris) had little alternative other than to leave the track because of the proximity of (Verstappen), who had also left the track."
Had Norris finished ahead of Verstappen, he would have reduced his gap in the championship to 51 points, gaining back three points after losing two to Verstappen in the sprint event on Saturday, which the Dutchman won with Norris third.
Norris said: "It’s a momentum killer, but we came here with our mind open, not expecting to dominate or win or anything.
"The fact Ferrari were so quick showed they are just as competitive, I could only have finished third. But the one guy I had to beat is Max and I didn't beat him. It was a non-successful weekend. But we gave it a good shot. I tried and we have work to do and I have work to do on myself.
"I respect the battle we had. Good one, enjoyable, respectful. Turn One, I didn't do the correct thing but I feel like what happened at the end was more on my side, but otherwise it was a good battle.
"We didn’t come out on top because I didn’t do a good enough job. If I defended better in Turn One and wasn't driving like a muppet, I should have led after Turn One and then we shouldn’t have this conversation in the first place."
Charles Leclerc is now 22 points behind Lando Norris in the drivers' championship
Leclerc dominated the race after taking the lead at the first corner and afterwards said he and Ferrari were now targeting the constructors’ championship after a strong run of races.
He also won the Italian Grand Prix in Monza, finished second to McLaren’s Oscar Piastri in Azerbaijan and was competitive in Singapore, the race before Austin, where he recovered to fifth place after starting 10th because of a mistake in qualifying.
Ferrari are 48 points behind leaders McLaren in the constructors’ championship, in which both cars score, and only eight behind Red Bull in second place.
Leclerc, who is 79 points behind Verstappen in the drivers’ championship, said: "We've got to target winning the constructors' title. It's an optimistic goal, but that's what we are here for.
"If we do everything perfect until the end of the season, no matter what McLaren does, if we do better than them, I think we can still clinch that title.
"With the drivers, I see it a bit in a different way. Even if we do everything perfect, I feel like it will require a little bit of luck inside that to try and get that title, and we cannot really rely on luck.
"So the drivers' seems to be quite unlikely, but again, I'll believe in it until it's mathematically impossible. But trickier."
Stella said he was not surprised Ferrari were quick in Austin, and that the track layout did not suit McLaren.
He added that McLaren had some upgrades coming "in the next two races, we will see if we are in condition to alter the competitiveness of the car."
Lewis Hamilton spun out on lap two in Austin
Mercedes were not in the fight at the front and endured a difficult weekend, Lewis Hamilton crashing on lap two of the grand prix at Turn 19, just as team-mate George Russell had in qualifying on Saturday.
Hamilton said the two incidents were similar and raised questions about upgrades the team had put on the car for Austin.
"I wasn’t even pushing at that point," said Hamilton, who started 17th but was up to 12th on the first lap. "I was just trying to get going.
"The front started bouncing and the rear end just came around same as George yesterday. P1, I had the same thing, spin in Turn Three, which is so rare, I have never spun in Turn Three all the years I have been here.
"If it didn’t happen that lap, it would have happened another lap because something wasn’t quite right there, and it’s been the same most of the weekend with this new package we had."
Hamilton said the team would have to consider whether to run the new parts in Brazil next weekend, although Russell cannot because there are not enough of them.
Russell recovered to sixth place in the race after starting from the pit lane driving a car rebuilt to a previous specification.
Team boss Toto Wolff said there was "not a fundamental issue with the upgrade" but he added that the team did not understand why their weekend had gone awry after they were competitive in sprint qualifying on Friday, when Russell was on the front row and Hamilton would have been on pole had he not encountered yellow flags on his lap.
Wolff also expressed his concern about the controversial ride-height altering divide that it emerged this weekend was on the Red Bull, saying it was "outrageous".
He added: "It’s not good enough to say 'that’s it, promise we’re not going to do it again'."
FIA single-seater director Nikolas Tombazis said on Saturday that the matter was closed after they put a seal on the device because the FIA could not retrospectively establish whether it had ever been used.