Formula 1 World Championship leader Jenson Button has confessed that Brawn GP 'doesn't have the pace' of rivals Red Bull Racing in the wet, after trailing in a distant third behind Sebastian Vettel and Mark Webber in the water-logged Chinese Grand Prix in Shanghai.

Despite having qualified only fifth, Button was widely expected within the paddock to make his way up the order on race day, by dint of having a heavier fuel load on-board his car than the top three on the grid. That, however, never materialised - indeed, far from it, with the British star the best part of ten seconds adrift of leader Vettel after as little as two racing laps in the torrential conditions.

Though he battled gamely, the Red Bulls were not to be denied, with an energetic duel with Webber midway through ultimately going the Australian's way, and Vettel forcing his way through and back into the lead later on - a move that signalled the beginning of the end of Button's hitherto unbroken winning run in 2009.

The warning signs, however, had been in evidence as early as the Malaysian Grand Prix in Sepang a fortnight ago, where Webber and Vettel were the fastest two drivers on the track when the rain was at its fiercest - and the former even fancied his chances of pipping Button to victory had the race not been red-flagged prematurely on safety grounds. After two outings of pure dominance, Button concedes, Brawn GP now has a challenge on its hands.

"First of all it's great finishing the race," the 29-year-old reflected after the chequered flag had fallen, "and in a way I'm really happy to get six points and be on the podium. It's the third step down, but to get through this race is an achievement in itself. It would have been so easy to throw it off by just trying to push that little bit harder, and I am so pleased that we got both cars to the end of 56 laps and scored as many points as possible.

"The conditions were pretty crazy, with rivers of water all over the circuit which changed every time you encountered them. The last turn particularly was like a lake, and you just couldn't brake for the corner. I was already pushing pretty hard and in turn one I had some massive moments, but I was always able to catch it and keep it on the road.

"I struggled with the car aquaplaning and the tyres shuddering as we couldn't get the temperatures high enough to make them work properly, and the problem is that even if you back off a little bit, you've got just as much chance to aquaplane and lose the whole race.

"They were really, really difficult conditions, and there were places on the circuit that you got to and just thought 'I'm going to go off this lap' - there was so much water, and you couldn't touch the brakes in those areas because you'd lock the rears or the fronts and be off the circuit. I know it's very difficult to see on TV the way it was, but for so many cars to finish the race I think is a credit to the cars and the drivers here.

"Mark Webber and I had a good fight for a few laps, but I just couldn't stay with him. We couldn't have beaten the Red Bulls - they were just too fast for us today, and when they got a gap of about 15 seconds, we knew that there was nothing we could do. Congratulations to Sebastian and Mark on a great result."

Button now holds a six-point advantage over team-mate Rubens Barrichello in the drivers' title chase, with Brawn's margin in the constructors' standings 16.5 - but the Frome-born ace knows that the Brackley-based outfit's rivals are catching up, and fast. Pinpointing the BGP 001's deficiencies compared to the Red Bull RB5 as its grip levels in high-speed corners, he insisted that a solution must be found if the team's world championship dream is to remain on-track.

"We obviously would have liked to have come away with the victory this weekend," the three-time grand prix-winner concluded. "In the dry I think we would have been a lot more competitive, but in the wet we don't have the pace compared to the Red Bulls.

"You can see it in the high-speed corners. When I was behind them - not for long, because they disappeared quite quickly - they can keep a really tight line, whereas we turn in and we end up on the outside of the corner because it feels like we're not going through the water; it feels like we're just floating across the surface of the water. That's something we need to look at - maybe we're just running the cars too low at the front and that's causing us an issue - because it's costing us quite a bit of time."