Sheila Farebrother explained her 64-year-old son has cut her out of his life "completely" after what was believed to be a disagreement with his partner David Furnish, with whom Elton fathers four-month-old baby Zachary.
She explained: "He has cut me off completely. It happened three years ago this June. He has had nothing to do with me since then.
"I don't want to go into what caused it. It is a painful subject. My son cut me out of his life for good."
The 86-year-old widower ' who is still financially supported by the singer ' also claimed she has "no particular interest" in meeting her new grandson, who was brought into the world via a surrogate mother on Christmas Day (25.12.10).
Speaking to The Sun newspaper, she added: "I have no particular interest really. You will have to ask them about that."
Despite Sheila having sold a treasure trove of Elton memorabilia for £28,820 when she recently moved house, she also insisted it had "nothing to do" with the rift between her and her son.
She said: "That has nothing to do with it. I moved into a smaller place and had nowhere to keep all that stuff."