Christian Horner 'wasn't invited to Jos Verstappen's birthday' after star driver Max's father called for him to resign... but one key Red Bull ally DID make the guestlist at the Dubai dinner

Christian Horner was not invited to Jos Verstappen's birthday party in Dubai on Monday evening amid a souring of relations, according to reports in Germany. 

The embattled team principal is thought to be at loggerheads with the father of Red Bull's star driver Max after they were spotted in a heated row after Friday's qualifying session for last weekend's Bahrain Grand Prix. 

Mail Sport reported exclusively that Verstappen Snr believes that the champion constructor will 'explode' if Horner does not walk away from his role at Red Bull in the wake of the toxic leaked WhatsApp scandal that has engulfed the paddock. 

Horner was cleared of misconduct following an independent investigation called by the team's parent company Red Bull GmbH last Wednesday but less than 24 hours later, an anonymously emailed leak of 79 documents appearing to show Horner sending sexually suggestive messages to the female employee at the centre of the investigation circulated amongst the sport's key figures. 

The 50-year-old and his Spice Girl wife Geri Halliwell put on a show of unity ahead of the first race of the season after the popstar flew to the Gulf state to watch Verstappen Jnr begin his title defence in Sakhir. 

Christian Horner was left off the guestlist for Jos Verstappen's 52nd birthday dinner in Dubai

The former Formula One driver called for his son's team principal to resign or risk the Red Bull project 'exploding'

The men were seen in a heated discussion after Friday's qualifying for the Bahrain Grand Prix

But there were no such niceties between Horner and the three-time world champion's father after the former was omitted from the latter's UAE birthday dinner. 

As per BILD, despite Horner also staying in Dubai before jetting to Jeddah for this week's grand prix, he was left off the guest list amid the tumult in the Red Bull garage. 

One key Red Bull figure present at the dinner will be of little surprise to those following the roiling civil war inside the British-based constructor. 

Dr Helmut Marko was invited to join in with the festivities due to his close ties to the Verstappen family - and his role at Red Bull could yet define whether Verstappen Jnr stays or leaves the team where he has made his name. 

The 26-year-old is thought to have a break clause in his £50million-a-year contract which is linked to whether Marko has a role at the constructor. 

Marko - Red Bull GmbH's motorsport adviser - is not employed by Red Bull Racing, but last season saw Horner held responsible for moves to sideline him at both Red Bull and sister team RB (then AlphaTauri). 

Red Bull's motorsport adviser was invited to the dinner in Dubai due to his ties to the family

Horner and his Spice Girl wife Geri put on a show of unity in the paddock over the weekend

Max Verstappen posted a touching tribute in honour of his father's birthday on social media

Verstappen Jnr advocated for Marko's eventual contract extension, which will keep the 80-year-old in his position until at least 2026. 

But should Marko take his leave from the team, the driver could yet make a shock move across the grid. 

His father was seen in conversation with Mercedes team principal Toto Wolff in Bahrain over the weekend, sparking speculation that Verstappen Jnr could take up the seat vacated by outgoing driver Lewis Hamilton in 2025. 

Horner is thought to have sought to broker peace with the Verstappens on Monday, taking a meeting in Dubai with his driver's manager Raymond Vermeulen. 

Neither Verstappen Jnr nor Snr were present for the conversation, but the peace talks are said to have gone smoothly. 

The team principal will only have to content with one member of the family in the garage at this weekend's Saudi Arabian Grand Prix, however, with Jos flying back to Europe to compete in a rally in Belgium. 

Verstappen took to social media to wish his father happy birthday on Monday, sharing photographs of the pair over the years with the message 'Happy birthday dad'.