Nico Rosberg had his Formula One world championship lead over Mercedes teammate Lewis Hamilton cut to one point after the German was demoted from second to third place in the British Grand Prix on Sunday.
- Lewis Hamilton wins British Grand Prix from pole
Race stewards imposed a 10-second penalty for receiving help from his team via radio transmissions, in breach of the regulations that state the driver must drive the car alone and unaided.
"Avoid seventh gear," Mercedes had told Rosberg.
"You need to shift through it."
Rosberg had finished the race, won by Hamilton for the third year in a row, 1.3 seconds ahead of Red Bull's Dutch teenager Max Verstappen.
He told reporters the gearbox would have failed without the instruction.
There are 11 rounds remaining. Rosberg reeled off four wins in a row at the start of the season while Hamilton has taken four of the last five.
Mercedes told Rosberg to avoid the seventh gear five laps from the end after he suffered problems, arguing after the race that the regulations allowed such advice if a terminal failure was imminent.
Team boss Toto Wolff read out part of the regulation on 'driver aids', saying the list of permitted messages included "indication of a critical problem with the car".
"That was the basis of our decision," he said, even as rivals questioned his interpretation.
Stewards said in their ruling that while the team "gave some instructions to the driver that were specifically permitted...the team then went further and gave instructions to the driver that were not permitted".
Mercedes said they intended to appeal the ruling, starting a process that could take weeks to resolve with a final decision made by the FIA's court of appeal.
Hamilton can meanwhile take the overall lead in the championship at the next race in Hungary on July 24.
