They claim the increasing amount of soft drinks drunk by children over the last 25 years has caused people to get fatter and has damaged their teeth.
A member of the CSPI has even set up a website asking Potter fans to join a 'Save Harry' campaign to stop any future connections with Coke.
But the protests do not appear to have hurt Harry Potter at the box office. Tickets sales from last Saturday alone have already overtaken the biggest-selling film of all time, Star Wars Episode I: The Phantom Menace.