There's no love lost between these two pop superstars.

Katy Perry was this week doing a UK BBC radio interview to promote her comeback single Chained To The Rhythm, when Ed Sheeran, himself at the radio station on promo duties, wandered past the studio.

"Oh babes! Thanks for keeping me off the number one spot, THANKS," she said, giving him the middle finger salute.

Perry's single has debuted in the top ten this week in charts worldwide, while Sheeran's single sits atop the singles chart in the UK, US and here in Australia.

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"Oh, you're so approachable, oh, you're everybody's best friend, ohhhh great," she drawled.

That wasn't enough to keep Sheeran from the studio - he came in and crashed the interview to reveal the first time he had ever met Perry, after a gig when he was still sweating profusely from being on stage.

"I walked up to her and I was like 'Hi!' and she said, 'I would hug you, but: EWW'," he revealed.

Perry's reaction to the anecdote was crude to say the least.

"Now that you're ED SHEERAN it's like, 'Put your ballsack on me'. Back then it was just Ed Sheeran, a guy with red hair who played guitar," she said.

Watch the full interview below:

Ed Vs. Katy