Fast-food chains are worried a new movie about their industry could damage profits, according to its director.

Speaking at the Cannes Film Festival – where Richard Linklater's Fast Food Nation is premiering – the filmmaker said it was already having an effect.

"They have hired agencies apparently that are going to be there when we come out as a movie in the States," he claimed. "It's a little interesting. I have never made a movie that is suddenly threatening somebody's corporate bottom line."

The film is a dramatisation of a bestselling book by Eric Schlosser and focuses on a fictional restaurant brand called Mickeys

Several actors who played Mexican immigrants working in a US slaughterhouse said they have given up burgers since the experience. Ana Claudia Talancon said: "Just the smell of being in there and the whole process was pretty bad."

Schlosser, who co-wrote the film with with Linklater, hoped it would encourage people to think about where they ate. He added: "By refusing to go to the fast-food chains, you're sending a message that animals shouldn't be treated that way, and workers shouldn't be treated that way."