Martin Whitmarsh on Friday said he is surprised one of F1's new teams for 2010 did not snap up the car built by Toyota.
Toyota elected to withdraw from the sport at the end of last year, but its Cologne headquarters had already penned a design for the 2010 season.
"Toyota built two cars that were available from Christmas, and I am rather surprised that some of them did not do that -- they rather looked a gift horse in the mouth," the McLaren team boss said at the launch of the MP4-25.
Ultimately, the complete TF110 was acquired by Stefan GP, but the Serbian outfit does not yet have an official entry to race in 2010.
However, the team announced on Friday that it has come to a "basic agreement" with Toyota "that Stefan GP will receive technical supports from TMG (Toyota Motorsport GmbH)".
Whitmarsh, who is also chairman of the F1 teams association FOTA, said it was "perhaps wrong" of Campos, USF1, Virgin or Lotus to turn down the Toyota car.
"Nevertheless they had their own reasons for that decision. We have to see in the coming weeks or months whether we can help those new teams to be there to add to the flavour and diversity of F1," he added.
Ferrari is pushing hard for three-car entries or customer cars to be allowed in F1, but Whitmarsh said he thinks teams should "develop their own cars".
"However, we are pragmatists and we have demonstrated in the past a willingness to provide customer cars. We remain willing," he added.
"I think we will do what we can (to help), but ultimately if there are teams that just don't have the capability or resource, or underestimated the task of being at the highest level of motor sport in the world, then some you can help and some you can't," said Whitmarsh.