The Hollywood sirens were tipped to star in period piece Tipping the Velvet, to be directed by Sofia Coppola.
Based on a raunchy Sarah Waters novel it tells the tale of an 1890s music-hall star and her female lover.
British newspaper the Daily Star claimed both Knowles and Longoria had confirmed the reports with the pop star, adding, "We've had Brokeback Mountain so the time is right for this divine novel to get the same treatment."
However, Longoria says, "Stop the madness. Believe me, I would love to work with Beyonce one day. She's so talented. But this is definitely not something we are doing together. It's completely and absolutely not true.
"What makes me crazy is that there are quotes out there, quotes from me saying it's true.
Knowles' spokesperson also confirms the story was false: "This is not happening. We've never heard of this film."
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