Ross Brawn has slammed the BGP001’s latest ‘improvements’, saying that they have made the car worse, not better.

Brawn GP were the runaway leaders after winning six of the opening seven Grand Prixs of the current campaign, but the three recent races has seen the team finish behind Red Bull, McLaren and even Ferrari.

The Brackley-based outfit's problem has been their tyres as Jenson Button and Rubens Barrichello have struggled to raise the temperatures of their wheels to optimal levels.

The problem has seen Brawn's lead in both Championships slashed dramatically with Button only 18.5 points ahead of Mark Webber while Red Bull are just 15.5 adrift of Brawn.

"It's true that the opposition has got a lot stronger, but in the first part of the season we were getting the most out of the tyres and unexpectedly we've had problems there (since)," team boss Brawn told the Gazzetta dello Sport newspaper.

"It's certainly related to some modification which we've introduced during the year and so we are analysing exactly every step we've taken to understand what has caused this problem."

The team's decline hasn't been helped by Formula One's ban on in-season testing, which prevents all the teams from running outside of grand prix weekends.

"I would be more comfortable if we had been able to do some testing," he said. "But this is a challenge which the regulations impose this year."

But it's not all doom and gloom for Brawn as Button's race engineer Andrew Shovlin is confident the BGP001 remains a race-winning car.

"We know the car is still quick," Shovlin told the BBC. "We just need to work out why it has become so sensitive to conditions.

"At the moment there is such a small window where it is working really well and we can't cope with that. We need to fix it so it's quick on any track and in any temperature.

"It's not as simple as going back to an old car specification. That's not the answer; it is something much more subtle than that.

"We may have done something to the car to make it more sensitive."