By GMM

The gap between BMW-Sauber and F1's two leading teams is "big" and wider than at the start of the 2008 season, according to former championship leader Robert Kubica.

The German team, and the Polish 23-year-old driver, have been much praised for their consistency near the top of the formula one field this year.

Following Lewis Hamilton and Kimi Raikkonen's Montreal pitlane crash, Kubica secured his and the Hinwil based team's first victory, raising the possibility that they are genuine contenders for the title.

But speaking with reporters at the Silverstone test this week, Kubica poured cold water on his chances by stating that he believes BMW-Sauber's rate of development in 2008 has not been fast enough.

"We didn't stay (with them)," he said, referring to the rival teams.

Kubica told the website of the British broadcaster ITV that BMW-Sauber was often among the pace of Ferrari and McLaren in the early races of this season.

"It looks like we didn't (improve) as much as them and the gap is pretty big - in Magny-Cours it was nearly one second," he said.

BMW-Sauber had its least competitive showing of the season at Magny-Cours last weekend, where Kubica finished fifth.

Kubica says the team took some wrong decisions in preparation for the French grand prix.

"So we should be back to normal pace (at Silverstone), which means still quite a big gap (to) Ferrari and McLaren," he added.

Kubica therefore plays down reports that he can regain his lead in the drivers' championship by the last race of the season in November.

"To be honest, with our car, even at full performance the best we can achieve (on merit) is fifth," he said.

"It's not enough," Kubica added, explaining that the current points standings is also a reflection of Ferrari and McLaren's technical problems and mistakes.

"That's why I'm still there, but if they start not having problems and not making mistakes it will be very difficult to keep up with them."