Scuderia Toro Rosso has hit back at Renault's suggestion that its recent reliability problems have been due to how the team operating its power units.
The Italian team has suffered a string of failures in recent races, with both Pierre Gasly and Brendon Hartley taking grid penalties for Brazil and then hitting further problems right at the start of practice.
Renault Sport F1 boss Cyril Abiteboul told Autosport on Friday that "we do have a little bit of a concern about the way that our engine is operated in the Toro Rosso car", before adding that there are "never coincidences in this sport".
In a statement issued on Saturday morning, Toro Rosso said the problems were nothing to do with the installation or how the team is operating the engine.
"It comes as a big surprise to the team that Cyril Abiteboul has suggested to the media that the problems Toro Rosso suffers with the power unit are primarily team related, and the way in which the power unit is operated in the STR12 chassis," read the statement.
"We would like to clarify that all the MGU-H and shaft failures Toro Rosso has recently suffered are not associated with how the team is operating or with how the power unit is integrated in the chassis.
"Nothing has been changed or altered in this installation during the 2017 season, other than cooling improvements mid-season.
"Since the summer break Toro Rosso has suffered continuous power unit related failures, and the resulting grid penalties has cost the team points and relative positions in the constructors' championship."
Toro Rosso is ending its Renault engine deal early to take up a Honda supply for 2018, and has loaned Carlos Sainz Jr to the works Renault team as compensation.
The team stressed that one of the big problems is that it has been forced to re-use old parts due to a shortage of new ones.
"One of the primary reasons for the issues we are seeing is the lack of new power unit parts available," the statement continued.
"In Toro Rosso's case the team is constantly having to change parts from one PU to another during the weekend and, on many occasions, is forced to run old specification assemblies.
"The last race in Mexico saw only two cars out of six finish the race, highlighting the poor reliability."
The team also made a reference to the battle for sixth constructors' championship, with Toro Rosso currently five points ahead of Renault.
Its statement ended: "We mustn't forget that they are fighting with Toro Rosso for a better position in the constructors' championship.
"As suggested by Mr Abiteboul the situation may not be a coincidence, but it is certainly not due to STR's car."