The comedian, who plays uncle Bryn in the comedy series - which is written by James Corden and Ruth Jones - said the series was “not a cinema thing.”
The series stars Mathew Horne and Joanna Page as the titular characters Gavin and Stacey, which is about two families from Essex and Wales who come together when the couple fall in love. Corden and Jones star as their friends as Smithy and Nessa - with Alison Steadman, Larry Lamb and Melanie Walters among Brydon’s co-stars.
The series aired between 2007 and 2010 - with it returning for a 2019 Christmas special. With 18.49 million viewers, it was the most-viewed non-sporting event in a decade and the most-watched comedy in 17 years.
Since the Christmas special, rumours have been rife that Corden and Jones would return with a film or another special.
Speaking to Digital Spy about the prospects of the film, Brydon, 55, said: “No, I don’t think they should do that. I think that would be a mistake. It’s not a film. It’s not a cinema thing. It is what it is, and I don’t hold film over television.
"There’s sometimes an assumption that if it were to become a film it would somehow be elevating itself, and I think that’s a misnomer. I think that’s a mistake."
He added: "I think that maybe, if James and Ruth decided to make another special, that would be wonderful.”
One of Brydon’s most memorable storylines is uncle Bryn and nephew Jason’s struggle to keep the events of their disastrous fishing trip a secret.
Exactly what happened on the trip is a running joke throughout the series.
About the fishing trip, Brydon said: “I don’t know. It’s never been told to me, and I don’t think Ruth and James know.
"I think it was always just a very funny idea they had, that wouldn’t it be funny if there was some elephant in the room, if there was some huge thing that hung over the family but was never talked about.
"We came close to hearing something in the Christmas special last year, where it looked as though Bryn was about the spill the beans…I think it would be a shame if we ever found out.”