New rumours of a film based on the BBC sci-fi drama emerged in November last year, with Harry Potter's David Yates reportedly attached to direct.
"I think it would take four or five years to get something like that off the ground, and I don't anticipate that I'll be playing the Doctor then," Smith told Collider. "My skin and the aging process couldn't take it."
He added: "For my money, whoever is playing the Doctor should be in the movie. I don't think there should be two Doctors."
However, Smith insisted that a Doctor Who film could work, suggesting that current showrunner Steven Moffat should script the feature.
"I don't see any reason why it couldn't work," said the 29-year-old. "I think they should get Steven to write it because he's the best."
Doctor Who will return to BBC One in August.
