Sinead O'Connor has threatened Miley Cyrus with legal action after she seemingly mocked the Irish singer's mental health issues in response to an open letter. Irritated by Cyrus' claims to Rolling Stone magazine that her new video for Wrecking Ball was inspired by her Nothing Compares 2 U promo, O'Connor penned a lengthy message to the 20 year old, urging her to stop prostituting herself. The former Hannah Montana star refused to heed the advice, and hit back on Twitter.com - likening O'Connor to troubled actress Amanda Bynes, before uploading a string of tweets O'Connor wrote during a meltdown last year (12), when she had attempted to take her own life while battling severe depression. Now in a second letter to Cyrus, O'Connor angrily accuses her younger peer of mocking the mentally ill, and has warned her to take down the tweets or face action from her lawyers. On Facebook.com on Thursday (03Nov13), she writes, "Miley... Really? Who the f**k is advising you? Because taking me on is even more f**kin' stupid than behaving like a prostitute and calling it feminism. You have posted today tweets of mine which are two years old, which were posted by me when I was unwell and seeking help so as to make them look like they are recent. In doing so you mock myself and Amanda Bynes for having suffered with mental health issues and for having sought help... "I am staggered that any 20 yr old woman of the 21st century could behave in such a dangerous and irresponsible manner as to not only send the signal to young women that its ok to act like prostitutes but also to the signal that those who have suffered or do suffer mental health problems are to be mocked and have their opinions invalidated. Have you no sense of danger at all? or responsibility? Remove your tweets immediately or you will hear from my lawyers. I am certain you will be hearing from all manner of mental health advocacy groups also. It is not acceptable to mock any person for having suffered." Unwilling to back down, Cyrus then replied via Twitter.com, writing, "Sinead. I don't have time to write you an open letter cause Im hosting & performing on SNL (Saturday Night Live) this week. So if youd like to meet up and talk lemme know in your next letter."