Button's hopes of a podium were undone by a lack of pace

"We were just not quick enough to challenge Ferrari and Renault," said the Briton, who drives for Honda.

"Those two teams have got it sorted because they are staggeringly quick in a straight line.

"We had no chance of overtaking and couldn't make it up in the corners. That was frustrating."

Button, who captured his first Grand Prix win in Hungary before the summer break, saw his chances of a second victory fade when he became entangled in a pile-up on lap one.

The chaotic aftermath of Giancarlo Fisichella's spin enabled Button to move up from sixth to fourth, but it also allowed the leading trio to pull away.

That was not the result we wanted David Coulthard

"The start was absolutely terrible," said Button. "We really have to work on it.

"I didn't lose my place luckily enough, but the first cars just disappeared.

"I nearly crashed into Fisichella at Turn One and after that it was all quite quiet for me. It was a pretty boring race from then on.

"We have to make some changes for Monza. There has got to be more to come."

David Coulthard will also be seeking improvement in Italy in two weeks' time after he was forced to retire his Red Bull with three laps remaining.

"That was not the result we wanted," the Scot said.