Sinéad O'Connor has threatened to sue Miley Cyrus after the American singer publicly mocked her in a series of Twitter posts and likened her to the actor Amanda Bynes, who has been undergoing psychiatric treatment.
Cyrus also reminded her followers on Twitter of O'Connor's past by posting a picture of her tearing up a photo of the then pope, as well as a screenshot of older tweets sent by the Irish singer during a period when she had been suffering from bipolar disorder and had asked her followers to recommend a psychiatrist.
The dispute comes after two days in which the 20-year-old former child star has become the subject of global attention following an open letter in which O'Connor warned Cyrus that the music industry could "pimp" her sexuality. Since then, amid a flurry of media reports and opinion pieces by observers across the spectrum, the public correspondence between the two women has taken an increasingly fraught turn.
Responding to O'Connor's initial anger, Cyrus had also tweeted: "Sinéad. I don't have time to write you an open letter cause I'm hosting & performing on SNL [Saturday Night Live] this week. So if you'd like to meet up and talk lemme know in your next letter."
In the latest escalation, O'Connor used Facebook to accuse Cyrus of "stupid and dangerous" behaviour and threatened to take legal action against the US star if she does not apologise publicly or remove the tweets.
"I have no interest whatsoever in meeting you. You had plenty of time yesterday to abuse Amanda Bynes … an entirely innocent party … and myself … who also did nothing to deserve your abuse," the 46-year-old said.
She complained of suffering enormous distress from what Cyrus had done and said that her actions had the potential to damage her career, since the American had deliberately given the impression that postings of O'Connor's tweets reflected her current condition.
"If you cannot apologise 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 went on: "When you end up in the psych ward or rehab I'll be happy to visit you … and would not lower myself to mock you. Be a proper woman and make the public apologies I have listed above. Your hosting SNL is a bullshit reason for not taking five minutes to do the right thing and your behaviour yesterday will rebound upon you very badly.
"You have no business abusing Amanda Bynes or anyone else. How do you think you made her feel yesterday? How do you feel when your friend Britney Spears is mocked and humiliated for having had mental health problems?"
In an earlier posting on Facebook, O'Connor wrote: "I do not at all support or condone the abuse or mockery of those who have been brave enough to openly discuss mental health issues.
"Mockery causes deaths. Period. It is an unacceptable form of bullying, no matter who is doing the bullying."
Cyrus, who is the daughter of country star Billy Ray Cyrus, has been engaged in rebranding her image since she found fame as the child star of Disney children's show Hannah Montana. She had come in for criticism in recent weeks for a number of controversial performances, including an appearance at the MTV Video Music Awards in New York last month.
Her public exchanges with O'Connor date back to a 1,000-word post, written on the Irish singer's personal blog, which was triggered in response to comments by Cyrus in a Rolling Stone cover story.
She explained that O'Connor's music video for Nothing Compares 2 U inspired her recent Wrecking Ball video, which begins with a tearful close-up of the singer. However, unlike the Irish singer's classic, the Cyrus video transforms into her posing provocatively in underwear and, ultimately, naked.
Written "in the spirit of motherliness and with love", O'Connor had pleaded with Cyrus to reconsider her career's projection in the run-up to her Bangerz album launch, suggesting that the people around her are monetising her "prostitution".
"I am happy to hear I am somewhat of a role model for you and I hope that because of that you will pay close attention to what I am telling you," she added.
Referring back to her iconic look in the Nothing Compares 2 U video – a huge international hit written by Prince – O'Connor admitted that she was asked by her label to reconsider her image for the 1990s video.
"The look I chose, I chose on purpose at a time when my record company were encouraging me to do what you have done. I felt I would rather be judged on my talent and not my looks."