Adding to what has been a season of disappointment, Max Verstappen was forced out of the Belgian Grand Prix with an engine failure when running fifth.

It was his fourth mechanical failure in a race this year, and his sixth retirement of the campaign so far.

Speaking to Dutch TV channel Ziggo Sport, Jos Verstappen said the situation was getting very difficult to accept – but he drew short of saying that the time had come to start looking for another team.

Asked if it as an option to leave Red Bull, the former grand prix driver said: "Maybe this is the wrong moment to ask this question, but you do start to question everything.

"I notice about Max that he's very disappointed. It's tough to keep yourself motivated the whole time when things are going like this.

"I mean, he's doing very well in qualifying, he's half a second quicker than his team mate and he's just behind the Ferraris.

"And then, after seven or eight laps, he's standing at the side of the track again. This should not be able to happen, certainly not at a top team."

Verstappen also moved to dismiss any suggestion that his son's driving style was contributing to the fact that he had suffered the brunt of Red Bull's failures this year.

"Max can't do anything. Max isn't doing anything wrong," added Jos "People are asking that question again if Max is being too tough on his equipment. But that's complete nonsense.

"He can't overdrive, he can't break the material. We all know what it is: it's just the equipment that isn't good enough."

When asked if there was still something to be salvaged, Verstappen replied: "This year certainly not.

"I think we all need to calm down for a bit and then maybe we need to sit down with each other because this won't last if things keep going like this."