McLaren's Martin Whitmarsh has admitted his team are not in a position to challenge for the Formula One world championship after a poor qualifying session for the British Grand Prix left Lewis Hamilton a lowly 10th on the grid and his British team-mate Jenson Button a disappointing fifth at Silverstone.

The stark acknowledgement of his cars' poor performance in the face of the Red Bulls' continuing dominance – Mark Webber qualified first and the championship leader, Sebastian Vettel, second – is certain to further darken Hamilton's mood. In a long statement, possibly designed to pre-empt further dissent from Hamilton, the McLaren principal said: "This team cannot be happy, we're not happy, were not content, we're disappointed. That's a fact and it's quite obvious. We did not put on a competitive showing in qualifying and we know that."

His team had suffered due to the weather and last-minute regulation-tweaking that plagued practice and qualifying but there were more fundamental issues at stake. "On the evidence of today our car is not quick enough. That's how it is," he said. "Do we concentrate on trying to win the championship? Well, frankly at the moment that's probably the wrong focus. It is: get back to being competitive as quickly as possible, win races and see where it goes from there."

Hamilton had already expressed his discontent before a decision to send him out on scrubbed rather than fresh tyres cost him dearly in qualifying, this time over the amount of sponsorship work he is required to do by McLaren.

The driver was upset by his workload in the runup to Sunday's race and is refusing to sign another contract unless McLaren scale back on the number of appearances they ask him to make. "You have to make changes," he said. "When I re-sign the contract with McLaren they are going to be shocked at how many days they are not going to be able to make me do. I will be doing a lot less work. I definitely won't be doing the whole period of time before the Silverstone grand prix, that's for sure. I will have at least five days to prepare [for the race] in the future."

Hamilton, who has had a torrid season on and off the track, has worked almost every day since the last grand prix, in Valencia two weeks ago. The British driver has sometimes had to make as many as four appearances in one day on behalf of McLaren's many sponsors. He said in the buildup to this grand prix: "I have just come from the last race and I have had a day or two off and I am certain if you look down the paddock there won't be many other drivers that have done what I have been doing over the last two weeks." He had been unable to train for the past two weeks, adding wryly: "But what's important is that the sponsors are happy."

Whitmarsh's statement did not address these concerns directly but he knows that performance on the track goes a long way to assuaging driver complaints about commitments outside the cockpit. "We've arrived at a situation where out car isn't quick enough and we'll do what we can to make it quicker," he said. "We're not giving up."

Formula One takes a four-week break next month and Hamilton is clearly in need of a time away from the paddock. "I can't wait," he said. "I am excited for the break. I haven't decided where I am going or what I am doing. But it is nice to know I have got that coming up." When the 26-year-old was asked whether he sometimes felt 30, he said: "I feel older." When it was suggested there was a danger of burnout, he replied: "Definitely."

Hamilton has embarrassed his employers on a number of occasions this season, particularly in Montreal last month when he stormed into the Red Bull motorhome and talked to the team principal, Christian Horner, about the possibility of switching teams. McLaren, though, pay their drivers handsomely for the PR work and Hamilton is in the penultimate year of a five-year contract worth £75m.

His McLaren team-mate Button said: "I echo Lewis's feelings, it has been busy. But it's the British GP so it is going to be the busiest week of the year for us."