In the motherly letter, O'Connor claimed that Cyrus is being ‘prostituted’ by the music industry and warned that she might end up in rehab.
'Have you any idea how stupid and dangerous it is to mock people for suffering illness? You will yourself one day suffer such illness, that is without doubt'
Cyrus – whose video ‘Wrecking Ball’ is reminiscent of O’Connor’s ‘Nothing Comapares 2U’ - dismissed the advice. She responded with a tweet that mocked the mental health issues O’Connor faced back in 2011. She likened the singer to Amanda Bynes – who was recently hospitalized after setting fire to herself.
She wrote: ‘Before Amanda Bynes.... There was....’ and linked to O'Connor's old tweets, adding a photo of the moment O’Connor tore up a photo of Pope John Paul II.
O'Connor then took to Facebook to defend herself, warning Miley she would end up with mental health issues herself.
She wrote: ‘Have you any idea how stupid and dangerous it is to mock people for suffering illness? You will yourself one day suffer such illness, that is without doubt. The course you have set yourself upon can only end in that, trust me.’
‘I am staggered that any woman could behave in such a dangerous and irresponsible manner as to send the signal to young women that its ok to act like prostitutes’
She added: ‘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.’
The singer then threatened that Cyrus would ‘hear from [her] lawyers’ if she didn’t remove the tweets.
Cyrus then issued two more tweets making fun of O'Connor's long letters with a reference to her hosting-and-performing gig on Saturday Night Live this week.
‘Sinead. I don't have time to write you an open letter cause I’m hosting & performing on SNL this week,’ she tweeted "So if you’d like to meet up and talk lemme know in your next letter. :)’
To read O'Connor's original letter in full, click here.