Honda on Monday accused MotoGP leader Valentino Rossi of deliberately making Marc Marquez crash in Malaysia in a claim that ratchets up the tension ahead of this weekend's title showdown in Valencia.
Rossi leads the 2015 championship by seven points from Jorge Lorenzo but must start from the back of the grid on Sunday after stewards in Sepang found him guilty of kicking Honda star Marquez off his bike.
Rossi is appealing the punishment with a hearing set to take place 48 hours before the race.
The Italian MotoGP legend's actions have caused widespread outrage in the Spanish media.
But Rossi denies kicking defending champion Marquez, claiming that he is the victim of a Spanish plot.
He accuses Marquez of pursuing a "dirty game" with the express intention of helping compatriot Lorenzo to the title, claiming Marquez conspired to help Lorenzo win points in Australia.
Honda stepped into the spat on Monday, the Japanese constructor claiming their technical data proves Rossi kicked Marquez's machine.
"It is clear that Valentino intentionally pushed Marc towards the outside of the track, which is out of the rules, therefore Marc had no other option other than to run wide," said Honda's vice-president Shuhei Nakamoto.
"The data from Marc's bike shows that even though he was picking up the bike trying to avoid contact with Valentino, his front brake lever suddenly received an impact that locked the front tyre, which is the reason for his crash.
"We believe that this pressure was a result of Rossi's kick."
Spain's secretary of state for sport, Miguel Cardenal, told Spanish media that he hoped "fair play" would rule at the MotoGP season finale on Sunday.
Rossi, seeking a record-equalling eighth premier class title, heads to Valencia on 312 points with Lorenzo on 305.