The 33-year-old has previously discussed an incident where she was abused by an industry figure in general terms.
Whilst Allen has often been vocal about sexual assault in the industry this is the first time she has shared details about her experiences.
In the interview Allen alleges that after getting "smashed" at a party, an industry executive put her to bed in his hotel room and left her to sleep.
Speaking to the Guardian, Lily told of how she awoke at 5am to "feel someone pressing their naked body against my back". I was naked, too.
Lily has address her feud with Cheryl
'I could feel someone trying to put their penis inside my vagina and slapping my arse as if I were a stripper in a club. "I found my clothes quickly ... and ran out of his room and into my own".
Lily did not report the matter as she was left feeling like she blamed herself over the incident because she had been drinking, and would be seen as "difficult" and "hysterical" if she went to police. "I wanted it on record that I'd been sexually abused by someone I worked with". Though the pop singer wanted to name him in her memoir, the publisher's lawyers advised her against it.
Allen says she later was offered a gig promoted by Radio 1 that would also feature one of the executive's artists, but turned it down. Allen claims she was subsequently "punished by Radio 1, with no airplay for my next single, Trigger Bang". "Let's try and teach our daughters to be stronger and more resilient, better at being less grateful, more insistent on being taken seriously, louder at saying no", she said. Still, she asserts that the music industry is "rife with sexual abuse", and "allows and sometimes even endorses toxic behaviour by men towards women".
She wrote: "It was consensual, sure. It's just that I was looking for help and he acted as if he was doing me a favour".