Mercedes' motorsport vice-president Norbert Haug has admitted that there are contractual reasons why his company will not be partnering Red Bull Racing in next year's Formula One campaign, despite rumours that the Milton Keynes outfit and Silverstone-based rival Force India are poised to swap suppliers.

The Spa-Francorchamps paddock was rife with suggestions that Force India would assume Red Bull's Renault engine deal, with its Mercedes link heading to the current championship leader, but Haug - and others - were quick to play down or dismiss the speculation. Red Bull, despite its lofty position in both sets of standings, has long been critical of the engine status quo which, it claims, sees it penalised by the Renault V8's supposed lack of performance, and was in negotiation to switch to Mercedes this season, only to have the Three Pointed Star's current client base object to further expansion of its roster.

Despite that, the rumours of a switch refuse to go away, but Haug was clear in his dismissal of the story.

"We would have worked with Red Bull already this year, but we have an exclusive contract with McLaren [and], understandably, McLaren has put in the veto," he told German television channel Sky on Friday, "We have to respect contracts, of course, and that is the situation.

"I would be very happy to see Mark Webber, who was formerly with us [in sportscars], and, of course, Sebastian Vettel, drive with our engines, but, at the moment, that is not the case."

Force India also denied the validity of the story, pointing out that it has a contract with Mercedes that runs until the end of 2012, and insisting that it is fully up to date with its payments to the German giant, while Mercedes team boss Ross Brawn claimed that he had been unaware of the suggestions.

"That's the first time I've heard the rumour, genuinely," he told journalists after practice in Belgium, "I wasn't aware of that rumour, and I don't think there are any plans for Mercedes Benz to supply more teams."

McLaren team principal Martin Whitmarsh, meanwhile, said that he had not been asked for his view on Mercedes expanding or changing its clients.

"I've heard the rumours, but that's it," he stressed, "I think we can continue doing the best job we can with a great engine that we have from Mercedes Benz, but I don't know of any plans [for change]. I haven't been consulted or asked - and nor do I necessarily need to be. I'm sure Ross is much closer to this than I am."