Helmut Marko has confirmed that Max Verstappen has a Red Bull exit clause and has fuelled fears that the Dutchman will quit. Verstappen has been frustrated with Red Bull's performance in recent months, having not won a race since the Spanish Grand Prix on June 23.

The 27-year-old has been linked with an exit from the team and was suggested as a possible replacement for Lewis Hamilton at Mercedes. However, that move did not materialise and the Silver Arrows have placed their trust in rookie teenage driver Kimi Antonelli.

But Marko has done little to calm speculation that Verstappen could still leave Red Bull in the future. The team's veteran adviser confirmed reports that the three-time world champion has a performance-related exit clause which could prompt him to quit - either the team or Formula One entirely - if he believes Red Bull are not making progress with their vehicle development.

“The danger is there,” Marko admitted to sport.de.

“Max is not the type to beat [Michael] Schumacher’s or [Lewis] Hamilton’s records. When he’s in the car, he wants to win. But the environment has to be right. If the whole thing no longer suits him, you can expect him to say from one day to the next: That’s it!

“Most top drivers have exit clauses that are performance-related. Max has one too. This means that if we can’t provide him with a car in which he can drive at the front, that is certainly something he will consider.”

Verstappen's previously huge lead at the top of the Drivers' Championship leaderboard has closed to 52 points ahead of Lando Norris. His previous dominance on the track has waned and after coming second behind Norris in Singapore, he urged Red Bull to find more pace.

"I have been saying for weeks that we need to bring more performance to our car and everyone in the team knows that as well," Verstappen said. "So far, it looks like everyone around us is bringing more updates than we do. Of course we have to work on that, we find more performance for our own car as well.

"At the moment we just lack some speed. The gap to Checo [Perez] is pretty big and I think that says a lot, because I don't think Checo has become worse."

Verstappen remains the favourite to win what would be a fourth consecutive world title. But there will remain concern inside the Red Bull paddock that their star driver does not see evidence of enough progress.