Grace Rwaramba - who has been the primary carer for the singer's three children for several years - is reportedly suffering from lupus and has been abandoned by the pop superstar in her time of need.
A source told the New York Daily News newspaper: "Grace is not doing well. She's ill, and she could use his spiritual, mental and financial support right now."
"I do believe Michael has affection for Grace, but he acts like a child. He could at least give her a call and say, 'How are you doing, Grace? Do you need more doctors?' But it's never like that. It's always taking."
"She's not on death's door, but she's like she was at the beginning of his child molestation trial when she took a break."
"Maybe he thinks she's on a similar break, and she just needs time to get well. I hope he can find it in himself to not be so self-centered."
However, Jackson's spokeswoman Raymone Bain has vehemently denied claims, insisting Grace is in good health.
Bain said: "This is a hilarious rumor. I can guarantee she is not very ill. I've spoken to her in the last two hours."
Bain refused to disclose the "Thriller" singer's current whereabouts, only saying "he's in the studio finishing up some music, doing vocals with a host of artists."
The spokeswoman also claimed Rwaramba, 40, is still the primary carer to 10-year-old son Prince Michael Jackson II, nine-year-old daughter Paris, and five-year-old Prince Michael Jackson III nicknamed "Blanket."
Last month, it was claimed Jackson and Rwaramba had married in Las Vegas but Bain has dismissed the rumors.
The eccentric singer has recently been dividing his time between Ireland and Las Vegas and was rumored to be planning a residency at a Las Vegas hotel.
In July, Jackson dropped his Las Vegas plans without any explanation.
