Lewis Hamilton believes McLaren are falling behind their rivals after a disappointing Monaco Grand Prix.
Hamilton qualified third but fell back in the race and finished fifth, while Jenson Button retired after crashing into Heikki Kovalainen.
"The team have definitely got some work to do because we are falling behind race by race," said Hamilton.
"The others are picking up serious pace. If we are not lucky then it will fall away from us too quickly."
Hamilton is now fourth in the championship, 13 points behind championship leader Fernando Alonso, while Jenson Button has dropped to seventh, 31 points adrift.
The 2008 world champion appeared reasonably happy with his performance when he qualified fourth, which was upgraded to third after Michael Schumacher's penalty.
But the McLaren driver made a poor getaway and then lost places to Fernando Alonso and Sebastian Vettel during the pit stops.
"It wasn't frustrating, it wasn't the best result," added Hamilton. "This is motor racing. I really dislike going backwards, but we still came away with some points.
"There are many races ahead of us and we still need to keep pushing.
"My start was one of worst starts I've had in a long time. I don't understand why it happens when two guys next to me and those behind us got perfect starts.
"I was fortunate not to get caught up in the crash. We do thousands of starts, it shouldn't be a problem.
"Then after that I don't know how long my pit stop was but I lost a lot of time. I wasn't able to keep up with Alonso, and Sebastian got me through his pit stop. Then it is impossible to overtake.
"It's not a great feeling but that's the way it is. Where was the rain when I needed it?"
Hamilton's team-mate Jenson Button had another frustrating race after a positive start to the weekend.
The 2009 world champion topped the times in second practice on Friday but was at pains to explain a loss of performance in qualifying, which saw him miss the cut in Q2, and then things got worse when he lost track position at the start of the race.
As a result, he spent much of the race behind the Caterham of Heikki Kovalainen, and after several failed attempts at a pass the 32-year-old collided with the Finn, spinning him out of the race.
"I couldn't wait for the race to be over," said Button. "We were so far behind the points. It's so frustrating when you are so much faster than the car in front. It's just one of those things.
"It comes from a bad qualifying and being unlucky at the start. That's what dropped me down so far.
"We need to be quicker in qualifying. I need to find a balance and a consistent car. At the start of the weekend it seems to be good and then in qualifying it's not. We need to find out why.
"Kovalainen is allowed to drive around how he wants. It's part of racing. I had to try to fight my way back but it was impossible. At the end I tried down the outside [of Kovalainen], I don't know if he moved across or what but I got a puncture."