Cyril Abiteboul has scoffed at Red Bull's optimism about life with Honda power.
Abiteboul is the boss at Renault, where he was at the epicentre of the French manufacturer's eventually poisonous relationship with Red Bull.
For 2019, Red Bull is finally leaving Renault to become Honda's new works engine partner. This year, the energy drink owned team has been hyping up expectations that life with Honda will be much better.
"Honda is still 20 kilowatts behind us," Abiteboul insisted, according to Marca sports newspaper.
"I know what Red Bull says but they're hiding the facts and manipulating the data. I understand their communication strategy, but there are no facts," he charged.
"Eventually it will be seen that Honda is 20 kilowatts behind and that they have not moved from their current position," Abiteboul added.
Red Bull's Dr Helmut Marko responded to Abiteboul's comments.
"We do not need to discuss that because next year we will see what our position is," he said. "Mr Abiteboul will continue to daydream but next year it will be completely clear."