Renault chief Cyril Abiteboul has accused Red Bull's Adrian Newey of lying after he blamed the car's performance on the engine.
Red Bull won four successive constructors' championships between 2010 and 2013 but were beaten last year by the Mercedes team of Lewis Hamilton and Nico Rosberg.
The Red Bull technical boss had previously stated that the engine, supplied by Renault, was "quite a long way behind, with all sorts of failings, and with no obvious light at the end of the tunnel".
Abiteboul denied the claims, telling Authebdo: "Adrian is a charming man and an engineer without equal but he has spent his life criticising engine partners.
"In addition to our problems, Red Bull has some chassis problems which don't help the situation.
"In particular, the lack of rear stability. These two problems combine to ensure the car is difficult to drive."
Daniel Ricciardo was lapped during the Australian Grand Prix by race winner Hamilton, with Daniil Kvyat retiring.
Jonathan McIntosh
