Nico Rosberg says teammate Lewis Hamilton was "extremely aggressive" in their first corner clash during the United States Grand Prix.
Rosberg started from pole, but Hamilton made a better start and dove down the inside at Turn 1, pushing the German wide.
As a result, Rosberg lost three places, but he went on to recover and looked set to win the race before a mistake near the end gifted Hamilton victory and his third title.
"Turn 1 for sure was very aggressive, what do I say? I haven't seen it, so I cannot comment it," Rosberg said after the race.
"For sure it was extremely aggressive.
"We hit each other. I would say Lewis came into me, which is not good, but I cannot say any more."
Having been quicker than Hamilton for most of the race, Rosberg scuppered his victory chances with a late off.
The German said he found the incident hard to explain.
"I am not saying anything was wrong with the car. I am assuming it was a mistake I made," said Rosberg.
"Getting too much wheelspin and getting away with the tyres not fully up to temperature. It felt strange as it had not happened to me before."