Kimi Raikkonen goes into this weekend's Belgian Grand Prix at Spa knowing he risks being written off as a title hope if he does not achieve the win that will revive his defence of his Formula One crown.

Raikkonen is without a victory since the Spanish round of the title chase eight races ago. More often than not he is being out-qualified and outpaced by Ferrari team-mate Felipe Massa and he has fallen 13 points behind championship leader Lewis Hamilton.

That series of lacklustre runs, not helped by a blown engine in Valencia a fortnight ago, has leading figures in motor racing questioning the desire of the 28-year-old Finn and prompted F1 great Niki Lauda to claim "Kimi's not really with it".

Bernie Ecclestone delivered a more withering observation when asked if Raikkonen, nicknamed Ice Man for his cool, emotionless demeanour, had fallen out of love with his sport.

"I don't think he's ever been in love with it," said F1's ringmaster. "Kimi is a super-talented driver and I just can't believe the way he's driving at the moment."

Former F1 driver Martin Brundle, now commentating for ITV, said: "I still believe that an on-form and onfire Kimi Raikkonen is marginally faster over a Grand Prix distance than Massa, but that is not the Kimi we have witnessed recently."

Raikkonen, the highest paid driver on the grid with an annual retainer of more than £10 million, has heard the whispers speculating his loss of competitive edge, and that former champion Fernando Alonso is eager to move into his car next season. He said: "If somebody has doubts concerning my motivation, let them doubt. One thing I can tell is, that right now I am more motivated than ever."

Yet Raikkonen did admit he must deliver again at Spa, where he has won the last three Grands Prix, saying: "I need it more than ever after the results of the last races."

Ferrari team principal Stefano Domenicali sought to excuse Raikkonen by claiming: "He isn't happy with the way the car enters the corners. He would like it more aggressive."

Brundle admits: "It may well be possible that the dynamics of the car and the behaviour of the tyres just don't suit Kimi, or he hasn't latched on to how to really make them work.

"His motivation can also be questioned by his general demeanour and his refusal to deny he might retire sooner rather than later.

"Kimi is very capable of blitzing Spa and making all these views redundant. But that will only serve to underline how much he's been 'missing in action' recently."