Hamilton was a lap down after sustainiAfter disappointing results in the European and British Grands Prix, McLaren returned to form with Jenson Button's second place at Hockenheim yesterday.
This was off the back of a major upgrade package, which included modified sidepods and exhausts that made the McLaren arguably the fastest car in dry conditions in Germany.
"It is good enough at the moment," said Whitmarsh when asked if the car is now strong enough to fight for the championship. "But it won't be [if we don't keep developing it] because we have half-a-season to go.
"Both of our drivers are capable of winning races and this year's world championship. The onus is on us to keep developing.
"We have a reasonable amount of momentum in the system at the moment. From what I have seen, that was the opinion of our engineers."
Whitmarsh refused to rule out either his drivers or the team making up big points deficits to get into the title hunt.
"Fernando is doing a great job and so is Ferrari but we are fighters so there will be some great races [to come] and we need to maximise our points," Whitmarsh added.
"He is a really strong competitor. In Germany, we could catch him and hurt our tyres, but we couldn't get past him. We were a reasonable amount quicker, but if you put someone like Fernando at the front of a race then you are going to have difficulty getting past him.
"Coming out of Melbourne, we were on a roll but Ferrari have turned it around. The same thing can happen [to us].
Whitmarsh admitted that McLaren's lack of performance on wet rubber in qualifying was a concern.
While Hamilton and Button were competitive on intermediate tyre during Q2, they were only seventh and eighth fastest in the top 10 shootout.
"It was just about temperature," said Whitmarsh. "The irony is that we came from Silverstone, where we were reasonable in the dry and pretty good on the wets but a disaster on the intermediates.
"Here, we were quick in the dry and the intermediates, but we didn't have it on the wets.
"These tyres have a small operating window and if you get into that, it is great. We are still learning [how to do that]."ng a puncture on debris early in the race, but was going faster than leaders Fernando Alonso and Vettel having just pitted for fresh tyres.
The McLaren spent a while between the first and second-placed Ferrari and Red Bull, while at the same time Hamilton's team-mate Jenson Button was closing in on Vettel, meaning Hamilton's presence helped his team-mate close the gap to the leaders.
"That was not nice of Lewis. I don't see why he was racing us," said Vettel. "If he wants to go fast he should drop back and find a gap. It was stupid as he was a lap down."
He added: "If you want to go quick and you have no chance to win the race you should respect that and use common sense. I didn't expect him to attack because I didn't see the point, and then I was surprised when he was side by side."
Vettel reckons the delay he incurred battling with Hamilton was critical in his loss of second place to Button in the subsequent pitstops.
"I think that [Hamilton battle] lost us the place to Button because shortly after that we pitted," said Vettel.
Vettel reclaimed the place with a controversial pass on the penultimate lap, but the stewards penalised him for the move and his 20-second punishment saw him drop from second to fifth.
Alonso acknowledged that Vettel's dice with Hamilton had been handy for him, and that he would have swiftly let the McLaren past if necessary.
"I knew that if Lewis was close enough with the DRS and trying to overtake, I had no problem to leave the space," said Alonso. "I knew he was not in the race. We didn't want to risk anything. For me it was a good position to have Hamilton between me and Sebastian.
"Having Hamilton there it meant Sebastian was 2.5s behind approaching the pitstop, so I tried to keep Lewis there."
Vettel also felt his Red Bull was not quite quick enough at times in the race, particularly when in traffic.
"Overall the pace was there but it was extremely difficult," said Vettel. "When we were close to Fernando and to Jenson we lost a lot and it was hard to stay close to try something under braking. That seemed to be the problem.
"I'm not entirely happy, because I think we could have been a bit better if we were in clean air for most of the race."