Red Bull magnate Dietrich Mateschitz has launched a scathing attack on beleaguered engine-supplier Renault for Red Bull Racing's significant drop-off in form in the last three races - a slump that looks likely to cost the energy drinks-backed outfit its chance of battling for the 2009 Formula 1 World Championship.

Following back-to-back one-two triumphs at Silverstone and the N?rburgring earlier in the summer - allied to the prolonged dip in performance endured by chief rivals Brawn GP and specifically Jenson Button - many in the F1 paddock suggested that RBR would be the team to beat over the second half of the campaign, and the favourites to steal title glory away from their Brackley adversaries. It has not, however, worked out that way.

Since last month's European Grand Prix, Sebastian Vettel has tallied just seven points and team-mate Mark Webber none at all, with the young German suffering a particular blow to his championship hopes with a double engine failure in Valencia, once in practice and then again in the race. With Button and Rubens Barrichello notching up respectively ten points and 22 over the same period - and breezing to a dominant one-two finish in the Italian Grand Prix at Monza last weekend - the momentum has swung firmly back in Brawn's favour once more, with a 40.5-point gap in the constructors' standings and nearest challenger Vettel now 26 markers adrift in the chase for the drivers' crown. Mateschitz is adamant as to where the finger of blame should be pointed.

"Actually it was [over] even before Monza," the Austrian billionaire told the Salzburger Nachrichten newspaper, when asked if the Italian result marked the end of Red Bull's 2009 F1 title charge. "It's because our engine is inferior to some of the competition, and the rules limit each driver to eight engines per season without testing.

"Of course, a race victory is not impossible, but that we can achieve upper positions with our two drivers four times is not expected. From now we can't even drive much in the practice sessions because we have no spare engines, which is a strange competitive condition.

"Our improvement this year was tremendous, but the best car and the best driver alone are sometimes not enough."

Indeed, Vettel enters the last four grands prix with the threat of a ten-place grid penalty hanging over him should the 22-year-old require a ninth engine this season. Red Bull has been linked with a move to Mercedes-Benz power in 2010, though rumours hint that a possible return to Ferrari is also an option on the table. Should the World Motor Sport Council (WMSC) find against Renault over the 'Singapore-gate' scandal next week, it has been mused that the French manufacturer could even be expelled from competition or else walk away from F1 of its own accord.