Red Bull Racing boss Christian Horner has warned that more manufacturers could leave Formula 1 if the FIA does not act on equalising engine performance.
Having pushed hard over the winter for the sport's governing body to ensure that the output of different engines in F1 was rebalanced, with his Renault power-unit believed to be behind the opposition, Horner fears that if the situation is left unchecked it could result in a single car maker dominating the season.
And he believes that could be the spur for rival manufacturers to leave the sport - in the wake of Honda, Toyota and BMW all having turned their backs on it over the last two seasons.
"The problem with the engine freeze is that you freeze in an advantage," he said at the launch of Red Bull Racing's new RB6 on Wednesday.
"I think the Renault has some good aspects and Renault, when the freeze came, took it a bit more literally than some of the other manufacturers. I think there is disparity currently within engine performance.
"On a fair and equitable basis, we rely on the governing body to ensure that you don't have large disparity between engines. Because the problem is that as the chassis converge in performance, the engines will become a key performance differentiator, and the idea of freezing the engine was largely to eliminate the performance differential between the engines."
He added: "I think the problem is if you don't allow some development, then you freeze in an advantage for one team or a disadvantage for another. So there has to be a balancing of that, otherwise we will end up with Mercedes-powered cars winning all the races - which I think is not good for F1. And other manufacturers may choose to leave F1 off of the back of that.
"The engine isn't supposed to be a key performance differentiator and therefore hopefully the ruling body will balance out somewhat the differences there at the moment."
Horner said that he was happy to leave the matter with the FIA, who made it clear last season that it was looking into the relative performance of the different engines.
"The FIA has all the facts and it is for it to deal with," stated Horner.
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