Renault has apologised for the two alternator failures over the Italian Grand Prix weekend, one of which put Sebastian Vettel out of the race, seriously compromising his defence of the title.

It a post race statement, Remi Taffin, the French manufacturer's head of track operations, admitted his company's failure.

"This weekend has not been acceptable from either a performance or reliability point of view," he said. "We have to apologise to Red Bull for the two failures on Sebastian's car, first in FP3 and now in the race. In both cases the alternator failed.

"We introduced a new spec' of alternator following the problems in Valencia and believed this would overcome the issues. We are still looking into why the part failed again here but we do know that even though the alternator was being operated entirely within the prescribed range, the part itself overheated and shut off the power supply. This is a priority between ourselves and our suppliers and we have to ensure we are fully on top of the problem before Singapore."

With Mark Webber also sidelined, albeit by a tyre wear issue, Red Bull boss Christian Horner was clearly frustrated. "It was a repeat failure on Sebastian's car with the alternator and we need to look into it and work with Renault to ensure it doesn't happen again.

"It's already cost us a victory in Valencia," he continued, "and now a points-finish again here in Monza. It's important we address it for the remaining seven races."