Swift's rep confirmed exclusively to WHO on July 13 that the singer wrote Harris' hit with Rihanna, and the Scottish producer quickly took to Twitter to tell his side of the story.
"I figure if you're happy in your new relationship you should focus on that instead of trying to tear your ex bf down for something to do," he wrote on Twitter. "I know you're off tour and you need someone new to try and bury like Katy ETC but I'm not that guy, sorry. I won't allow it."
Though neither has commented directly on the rumored feud, Swift told Rolling Stone in 2014 her song Bad Blood was written about a female musician who was a "straight-up enemy," and Perry allegedly responded on social media, tweeting "Watch out for the Regina George in sheep's clothing."
Perry also jumped into the tense Twitter back-and-forth between Swift and Nicki Minaj last year after the duo had a short-lived debate over the MTV VMA nominations.
"Finding it ironic to parade the pit women against other women argument about as one unmeasurably capitalizes on the take down of a woman…" Perry tweeted after the exchange.