Singer Sinead OConnor has threatened to commit suicide if she doesn't get her younger children back.
She said child and family agency Tusla will have a celebrity "death on their hands" if they continue to keep them from her, reports mirror.co.uk.
The mother of four took to Facebook last week threatening she would attempt to take her life if the State body does not allow her access.
The 50-year-old had been based in Chicago for most of last year following a reported suicide bid in Ireland days before Christmas 2015.
She sparked more concern last year when she went missing for 24 hours on a bike ride around Chicago city but was later found safe and well. She now lives in New York.
She has three sons and one daughter. Jake Reynolds, 30, is her eldest, followed by 21-year-old Roisin Waters plus two others who are minors.
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She wrote: "Open letter to the Irish State and its torture wing, Tusla.
"If matters are not corrected and I am not restored to my child and unconditionally apologised to by the State for what Tusla have most illegally, and with gross unconstitutional discrimination, put me through as a parent who suffers from mental illness.
"Then I promise you in the name of God, I will become the first Irish citizen to take their life in protest against Tusla on behalf of all mentally-ill parents. Who have been similarly tormented.
"You'll have a dead celebrity on your hands, and a lot of explaining to do. I will not go quietly. But I will go. After all documents are published which show what has been done to me if things continue as they have been for 18 months.
"You have left me with nothing to lose. I cannot be what anyone, including my employers, my children, my family or friends, needs me to be if I am not restored to my child. One would have thought that ought have been obvious to The Child and Family agency all along."
O'Connor, who has suffered gynaecological problems for years, underwent a hysterectomy almost three years ago.
--IANS
nn/rb