But the so called feud between the friends is nothing more than a play fight, it seems, after Katy jokingly threatened to spank Miley next time she sees her.
Katy tweeted: "Oooo gurrrl I'm gonna give you the BIGGEST spanking when I see you in the UK bb!"
The banter started after Katy told during an appearance on Australian TV of her shock when Miley tried to kiss her during a concert.
She told presenters on morning TV show Sunrise: "I just walked up to her to give her like a friendly girly kiss, you know, as girls do, and then she like tried to move her head and go deeper and I pulled away."
She added: "That tongue is so infamous!"
Miley responded: "Girl if ur worried abt where tongues have been good thing ur ex boo is ur EX BOO cause we ALL know where THAT's been."
The Wrecking Ball singer followed this up with: "Dontchyouuuu act like you didn't lurvvvvv it @katyperry."
It wasn't clear whether Miley was referring to Katy's ex husband Russell Brand, or John Mayer – with whom Katy is rumoured to have split.
Either way she seems to have taken Miley's jibes good naturedly, judging by her response.