His remarks came after Weinstein reportedly refused to appear in a documentary which Baldwin is currently filming at the Cannes Film Festival.
According to The Hollywood Reporter, Baldwin walked into the Calvin Klein IFP party in Cannes last Thursday (May 17) and proceeded to rant at length about Weinstein in front of attendees.
"I don't care who knows," he is quoted as saying. "After the success he had at Cannes last year and all the f**king Oscars, he's still a f**king douchebag. I can't believe it."
Director James Toback's documentary Seduced and Abandoned began life as a mockumentary but has become a more serious project about the process of financing films at Cannes, in part because many big names refused to participate in its former incarnation.
Francis Ford Coppola, Nicole Kidman, Marion Cotillard and Roman Polanski have all been interviewed for the film
A source close to Baldwin refuted the report, claiming that the actor had called Weinstein an asshole, rather than a douchebag.
His NBC series 30 Rock has been renewed for a final 13-episode season.
Watch a trailer for Baldwin's upcoming comedy Rock of Ages below: