McLaren's Kimi Raikkonen vented his frustration after engine failure ended his European Grand Prix on lap 10 when he was running in second place. He said: "I'm extremely frustrated and disappointed - I was at the front after getting past Takuma Sato and Jarno Trulli on the first lap.
"There was no doubt that things were looking good.
"We are making progress, but it's clear that we have to improve our reliability dramatically."
Raikkonen's team-mate David Coulthard had his race ended on lap 26 with the same problem.
The Mercedes-powered team have been under pressure this season after a string of poor performances.
McLaren have not scored a point in the last three races, and have only one point from the last five.
Coulthard, who had moved up to ninth after starting from the back of the grid, said: "Nobody in the team is enjoying the situation at the moment.
"But we will all continue to work hard to make things better and I'm confident that we will fight back."
And team boss Ron Dennis vowed to make McLaren competitive again.
"It's painful not to finish races, but the most constructive way forward is to analyse the problems and execute the engineering solutions," he said.