Pop star Katy Perry has jokingly branded Niall Horan a "stage 5 clinger" after crossing paths backstage at The Voice Australia.

The Roar hitmaker recently suggested the One Direction boy band singer had been trying desperately to flirt with her and score her phone number during their previous encounters, prompting Niall to issue a public plea to Katy to "stop being mean" to him.

"She's just finding any excuse now to just patronize me and go around spreading rumors about me," he told Australia's The Project TV show on Thursday (29Jun17). "I just want to be your friend!"

Katy, who has been single since splitting from British actor Orlando Bloom earlier this year (17), continued to tease fans about her relationship with the 23-year-old on Friday (30Jun17), when she featured on the same program and noted their nine-year age difference.

"(Niall) wants to go out on a date," the 32-year-old told viewers. "Have you ever seen the movie, The Graduate? That's kinda what it feels like. I could be his mom!"

After trading friendly barbs in the press, the two singers met up on Sunday (02Jul17) as they both appeared as guests on talent show The Voice Down Under.

Katy, 32, shared footage of their get-together backstage on her Instagram account, as she pretended to call Niall out for stalking her.

"You're following me!" she quipped in a video post, over which she had written, "@niallhoran stage 5 clinger".

"I am... everywhere," Niall responded as he pulled a silly face for the camera.