Vettel raced for Red Bull from 2009 to 2014, where he worked with team principal Christian Horner.

In February, Horner was cleared by an internal investigation into his behaviour towards a female colleague.

Allegations of inappropriate and controlling behaviour had been made against the 50-year-old, who denies wrongdoing.

Vettel acknowledged he was still in contact with Horner but “doesn’t know what did happen and didn’t happen” and “you never know what source to trust” with correspondence between the pair kept to sporting matters.

He said: “There were two races at the beginning of the season and they did great so I sent him [Horner] a message and congratulated [him], like other people in the team as well.

“From a sporting point of view, the team is doing amazing.”

Vettel said he is uncertain what the future holds for world champion Max Verstappen at Red Bull and did not rule out him leaving the team.

Verstappen said last month his father Jos was “not a liar” after the latter’s claim that the controversy around Horner was “driving people apart”.

The 26-year-old Dutchman dismissed claims in the media that he could be tempted to leave Red Bull for Mercedes in the wake of the Horner controversy.

“So many things happened in the last couple of months. I didn’t think there was any chance Lewis [Hamilton] leaves Mercedes and we were all taught wrong,” Vettel added.

“Exciting for the sport that he [Hamilton] does and as for what Max is doing you’d have to ask him, but it seems like anything can happen.”

Vettel also said it was “exciting” that F1 has worked to develop a synthetic sustainable fuel to be introduced in 2026, as part of its programme to be net-zero carbon by 2030, but it was long overdue.

He said: “I think it’s important we demonstrate there are solutions and there are options we can take, alternatives, because you cannot hover around on based on fossil fuels forever.

“I felt it’s a bit late because the technology has been around for way longer, but anyway here it is so it’s good to do that step finally and it’s an absolute must.”