Red Bull are my only threat, insists Ross Brawn

And Brawn praised his former employers for "the huge step from where they were at the beginning of the season".

But he warned they still had a lot to do. "You don't know if this is a one-off and merely a circuit that suited them better," he said. "They've still got work to do to start thinking about winning races."

The only other driver to have won this season, bar Button, is Vettel, taking victory at a rain-affected Chinese Grand Prix.

For the second successive race, however, the German was held up by Ferrari and was unable to show his true potential.

"Things could have been very different for them in the championship standings had Ferrari not held them up," said Brawn. "They're a big threat and I don't think we've seen their full pace."

However, Brawn insisted there was still more to come from his team. They are planning minor upgrades for both Monaco a week on Sunday and Britain on 21 June but have a more major overhaul lined up for the German Grand Prix on
12 July. And Brawn is confident it will keep them ahead of the chasing pack for the remainder of the season.

"You never completely know what's going to happen," he added. "We've got a group of people, they are working hard. They've all got a target for the German Grand Prix and the past history is they make it. That's when the major upgrade will come."

The biggest problem facing Brawn seems to be the potential fall-out between Button and team-mate Rubens Barrichello.

Barrichello, who quit Ferrari after playing second fiddle to Michael Schumacher under Brawn, has threatened to walk out on the team if he believes they are favouring Button over him.

The Brazilian had looked favourite to win in Barcelona after an electric start but he was outdone by Button, who was changed to a two-stop strategy during the race while Barrichello remained on a three-stopper, leading to suggestions the team had done so to aid Button's championship cause.

And Barrichello warned: "If I get the slightest sniff of the fact that they have favoured Jenson, I will hang up my helmet tomorrow. But I know Ross wouldn't do that. He asked me to drive for him and he knows I want to race fairly with Jenson."

Brawn, in turn, laughed off suggestions of favouritism within the team.

The 54-year-old insisted: "There is no priority being given and I'd love to see Rubens win a race and see his crew win a race because it would be really great for the team.

"You saw with Rubens' pass at the first corner that we have no team orders. He flew past Jenson and we were perfectly happy about that."