The 'Nothing Compares 2 U' singer says she was forced to call the police and to change the locks of her home in Bray, Co. Wicklow, Ireland, as she is terrified of the "very dangerous individual."
The 47-year-old star, who has four children, Jake, 27, Roisin, 18, Shane, 10, and Yeshua, seven, from previous relationships, penned a lengthy post, titled 'Dear Ravey Dave,' on her blog today (19.09.14), appealing to the man to leave her and her family alone.
She wrote: "I have two small children living in my house. How is it pleasing to you to be scaring a single mother?
"I would prefer not to feel frightened walking across my garden at night. I have repeatedly asked you to stop harassing me and you will not."
Sinead broke off her relationship with the man, who she does not name, two months ago after dating him on-and-off for two years, and claims she has been bombarded with "abusive emails" from him since then.
She added: "I have repeatedly asked you to stop harassing me and you will not. I have broken with you approximately six times. Each time you have bombarded me similarly.
"And like all abusing men, you have written me almost exactly the same 'apology' letters afterward. 'I'm so ashamed. I'm appalled I could have behaved that way.' Etc, etc, etc."
The singer is now worried about being attacked in her home.
She wrote: "Not that you had yet got to lay a hand on me. You've done it with words instead. But you might one day go further. Yes you might."
But she insists she is "not a woman to be bullied," and is urging him to seek help.