Miley Cyrus and Katy Perry used to be cool with each other, but these days they are in a full-on feud over the "Wrecking Ball" singer's attempt to slip KP the tongue during her L.A. show for her Bangerz tour.

The twerking queen leaned in for a smooch from the "Dark Horse" singer, who was sitting front row, but then tried to take it a step further, upon which the brunette beauty turned away.

"I just walked up to give her like a friendly girl kiss, you know, as girls do. God knows where that where that tongue has been. We don't know. The tongue is so infamous!" she told an Australian TV station.

Miss Miley had quite the comeback to her diss, though!

"Girl if ur worried abt where tongues have been good thing ur ex boo is ur EX BOO cause we ALL know where THAT been," the 21-year-old fired back on Twitter.

The claws are definitely out!

Update: Following the low blow, Miley tweeted "Dontchyouuuu act like you didn't lurvvvvv it" along with artwork of the duo kissing. Katy took the high road and playfully responded with, "Oooo gurrrl I'm gonna give you the BIGGEST spanking when I see you in the UK bb!"