Button's championship lead is down to 18.5 points
Jenson Button has admitted it is 'inevitable' that Red Bull will overhaul his Brawn's world championship lead if his team do not improve.
Button saw Red Bull rival Mark Webber cut his lead to 18.5 points with third place in Hungary, Button was seventh, his lowest finish of the season.
"We are leading the championship but its inevitable they will overtake us if we keep going like this," said Button.
"I've lost 15 points to Webber over the last three races and that's massive.
"It's five points a race. He will be in front of me in four races time. There are seven left so it's for sure not comfortable, but I can't do anything about it at the moment.
"It's like wearing the yellow jersey knowing that when you get to the mountains you are going to be useless."
Button won six of the first seven races of the season to establish a commanding lead in the drivers' world championship but has struggled with tyre problems since his last win in Turkey.
During Sunday's race, Button was heard asking his team over the radio: "How can this car be so bad at the moment?"
He said later: "Our car isn't driving as well as it did at the start of the season. There's obviously an issue."
Car 'is not what it was' - Button
Button's day could have been worse had either of his closest challengers, the Red Bull pair of Sebastian Vettel and Webber, taken the 10 points available for a race win.
Instead, Vettel retired with damaged suspension and Lewis Hamilton sprung a surprise by taking victory in his much-improved McLaren.
Hamilton could now be a crucial figure in Button's title challenge in the remaining seven races of the season.
At the British and German Grands Prix, Brawn believed their tyre problems were caused by the cooler conditions but in warmer weather at the Hungaroring, they again toiled.
"We keep complaining and saying its the weather's fault but it basically is," said Button.
"We've got a car that looks after its tyres when it's in the right temperature range but as soon as it drops out of that we've got a problem.
"We can't blame the weather in a way," added Button.
"It's our fault for building the car the way it is and we've got to work out what we can do to make it work in conditions that don't suit our car so much.
"Many of the teams at the front have improved their cars but, forgetting them, our car does not feel the same as it did three races ago. So there are lots of areas we need to look at."
Button's boss Ross Brawn said the team would attempt to solve the problem ahead of the next race in Valencia on 23 August.
"We again had problems with tyre temperature and graining in the race," he told BBC Sport.
Back to the drawing board for Brawn (UK users only)
"We can't do lap times consistently at the moment. It's completely different to how it was at the beginning of the season.
"We have to unravel what we've done in the last couple of races and understand if we've done something which has exacerbated the problem.
"Obviously other teams have gone forward, and your comparisons change, but we're getting problems you never saw in the earlier races."