Sinead O'Connor threatened to take legal action against Miley Cyrus after their feud on Twitter and Facebook.

O'Connor told Cyrus on Facebook to apologize or she'll sue. "If you cannot apologize I will have no choice but to bring legal proceedings against you since it is extremely hard to be given work when people think one is suffering from mental illness," she said. 

The two singers have been going back and forth since Miley Cyrus told Rolling Stone magazine O'Connor's video for Nothing Compares To You was the inspiration for her controversial Wrecking Ball video.

O'Connor responded with an open letter to Cyrus on Facebook and said, "I am extremely concerned for you that those around you have led you to believe, or encouraged you in your own belief, that it is in any way 'cool' to be naked and licking sledgehammers in your videos. It is in fact the case that you will obscure your talent by allowing yourself to be pimped, whether it's the music business or yourself doing the pimping."

Miley Cyrus then took a shot at O'Connor and posted a series of tweets from two years ago when O'Connor was having a mental breakdown and suffering from bipolar disorder. She referenced Amanda Bynes who was diagnosed with the mental condition earlier this week. The two went back and forth and O'Connor called out Cyrus on Facebook for mocking those who suffer from mental health conditions. Bipolar disorder advocacy groups have also called out Cyrus for her tweets. Cyrus took to Twitter to respond and suggested the two meet face to face to solve their issues.

"Sinead. I don't have time to write you an open letter cause Im hosting & performing on SNL this week. So if youd like to meet up and talk lemme know in your next letter. :) "

But that might not stop Cyrus from taking another jab. A source told Hollywood Life that Cyrus plans "to go after Sinead O'Connor during 'Weekend Update' or her monologue and she will most likely rip a picture of Sinead O'Conner on SNL," the source reveals.

Tags: Miley Cyrus Sinead oconnor