The Milton Keynes squad is suspicious about the straightline speed gains Mercedes has made in recent events, with Red Bull team principal Christian Horner describing Lewis Hamilton’s car as “unraceable” at the Sao Paulo Grand Prix. 

During the FIA press conference in Qatar on Friday, Horner challenged Mercedes boss Toto Wolff to explain the “score marks” on Mercedes’ rear-wing end-plate.

Wolff responded saying: “I think it is within what is allowed and therefore that’s okay.” 

Red Bull raised its concern with the FIA in Brazil last weekend but initially ruled out a protest. However, Horner confirmed Red Bull will not hesitate to launch a protest across the final three races of the season.

“Make no bones about it, if we see it on the car here it will be protested,” Horner told Sky. 

“It’s probably less of a factor here although we obviously saw significant straight-line speed in that session again, probably a 7kph difference between our cars. 

"But particularly Jeddah and Abu Dhabi you could have a situation like Brazil where the car is quite simply unraceable.”

Horner admitted Red Bull believes Mercedes is somehow managing to dump drag on the straights even when the Drag Reduction System (DRS) is closed and suspects it is doing so via a unique “hidden” design element. 

“There’s very specific regulations about this,” said Horner. “Obviously the directives that came out prior to Azerbaijan had material effect.

“I think this is something even more advanced, it’s hidden in the way that it operates so it’s harder to spot from a camera. But you can see the straight-line performance since Hungary, and particularly in the last two grands prix, has gone exponential.

“That obviously concerns us. And that’s why Adrian [Newey] and Paul [Monaghan] have been discussing it with the FIA.”

Asked how close Red Bull are to a protest, Horner replied: “We’ll follow the situation and it will depend really on what happens this weekend, what we see and the analysis that we’ve conducted. 

“So it really depends what we see, and it’s not just applied to here because I think it’s in many respects even more pertinent to the two circuits that are coming up. 

“But as a competitor, as I’m sure Mercedes - and we know - have paid a huge amount of attention to our car throughout the season and we’re obviously doing the same. 

“Obviously it’s high stakes, there’s an awful lot to play for and we just want to make sure it’s an equal playing field.”