SAO PAULO (Reuters) - Toro Rosso hit back at engine supplier Renault on Saturday over a spate of costly failures and suggested they may not be unrelated to the battle for sixth place in the Formula One championship.
Red Bull-owned Toro Rosso, who are switching from the French manufacturer to Honda power next season, are sixth with two races remaining while Renault's works team are seventh and five points behind.
Toro Rosso's French driver Pierre Gasly and New Zealander Brendon Hartley both have grid penalties for Sunday's Brazilian Grand Prix due to engine problems that have plagued them throughout the weekend.
Both also suffered power unit problems in Mexico two weeks ago, a race won by Dutch 20-year-old Max Verstappen in a Renault-powered Red Bull.
Renault Sport F1 head Cyril Abiteboul said at Interlagos on Friday that he had "a little bit of a concern about the way that our engine is operated in the Toro Rosso car".
The Frenchman, whose team took highly-rated Spaniard Carlos Sainz from Toro Rosso in October in return for ending the engine deal, added that there were "never coincidences in this sport".
Toro Rosso issued a strongly-worded statement ruling out their car or operational processes as a factor.
"Nothing has been changed or altered in this installation during the 2017 season, other than cooling improvements mid-season," the team said.
"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 pointed the finger at a shortage of new parts, with the team having to re-use components or run old specification assemblies.
The team also pointed out that only two of six Renault-powered cars finished in Mexico.
"We mustn’t forget that they (Renault) are fighting with Toro Rosso for a better position in the Constructors’ championship," the statement added.
"As suggested by Mr Abiteboul the situation may not be a coincidence, but it is certainly not due to STR’s car."
Red Bull principal Christian Horner told Sky Sports television that he was not involved in the dispute but understood frustration was mounting at a key stage in the championship.
"Reliability has been poor, we all know that," he said. "And there's a lot of frustration creeping in and it looks like it has boiled over."
(Reporting by Alan Baldwin in London, editing by Ed Osmond)