Mark Webber: "Ferrari, Lotus - compared to Mercedes - I think the Lotus is the most stable car" © Sutton Images Enlarge

Mark Webber believes Lotus is the biggest threat to Red Bull despite Mercedes' recent improvement in form.

Mercedes has had a very quick car over one lap all season but has struggled to make its tyres last in order to be able to display that pace in races. However, it has made progress over the last three races with Nico Rosberg winning at Silverstone and Lewis Hamilton victorious in Hungary, but Webber believes Lotus is the more consistent contender.

"I think we had Mercedes covered at the Nurburgring," Webber said. "Budapest; Lewis is very special at Budapest, there's no driver that can really touch him there in my opinion. Whereas at some other tracks he's not that strong, but in Budapest he's very, very strong. He proved that in a s**tbox McLaren as well, so when he won in the McLaren he was very, very strong. He's been quick there and he proved that again in the Merc; it was a good win for him.

"Ferrari, Lotus - compared to Mercedes - I think the Lotus is the most stable car across all tracks. Obviously they've been very, very good but just lost a little bit here and there. They've been very strong and a real threat throughout and Ferrari and Mercedes a little bit more [up and down]. I think Red Bull and Lotus have probably been a sniff more consistent at this stage."

Asked for his views on the possibility of Kimi Raikkonen joining Fernando Alonso at Ferrari next season after talks with Red Bull broke down, Webber admitted it would be an exciting prospect.

"Sensational team, it would be a brilliant team. Yeah, I think that would be good, it's just a question then of who goes to Lotus."

Asked about tension between two strong drivers at Ferrari, Webber added: "I think it would be OK."