Kelly Osbourne -- Paps Call BS ... We Weren't Aggressive, She FELL!

Kelly Osbourne fell flat on her ass all by her lonesome ... and Kelly is full of crap when she says the paparazzi pushed her to the ground ... so claim the photogs.

Osbourne was photographed leaving a restaurant/bar in London Tuesday night with boyfriend Ricki Hall. The photos tell the story ... she ate it big time.

Kelly took to Twitter, claiming she got "pushed by paps." But the photogs on the scene tell us … she looked "a bit worse for wear" and slipped. We're guessing the American translation for "worse for wear" has something to do with alcohol.