|© Renault Sport F1
The Renault engine supply team that powered Sebastian Vettel to four successive Formula One championships announced a major reshuffle on Thursday after mounting criticism from Red Bull.
The most dramatic move saw Renault Sport F1 president and managing director Jean-Michel Jalinier resign and retire.
He was replaced by Jerome Stoll, who becomes president, and former Caterham team principal Cyril Abiteboul, who will be managing director.
The changes came after Red Bull boss Christian Horner described the engines supplied by Renault this year as "unacceptable."
Vettel has suffered three retirements this year and been unable to mount a serious bid to retain his crown, as Mercedes duo Nico Rosberg and Lewis Hamilton have dominated the title race.
Stoll and Abiteboul will concentrate on delivering a competitive Renault engine in 2015. Teams are not allowed to change engines in mid-season.
Horner said the 2014 Renault engine has been as much as "80 or 90bhp" down on the Mercedes.
He added the French company was also under-prepared for F1's new era with 1.6-litre V6 turbo-charged engines.
Ferrari has also declared itself frustrated by a lack of power, as it has fallen behind Mercedes.
Renault F1 deputy managing director Rob White admitted they were behind their goals and added "therefore I cannot be satisfied."
"We were not quick enough on the track to respond or to satisfy our teams. ... We would have liked to have done things differently and achieve a different outcome."