The 'Thriller' hitmaker - who died in 2009 - was extremely close to Bubbles and allowed him to live a life of luxury at his Neverland ranch when he was alive.
However, since Michael's death, Bubbles has reportedly been neglected by Michael's family and don't contribute to the chimp's $20,000 -a-year upkeep.
Patti Ragan, founder of the Center for Great Apes in Wauchula, Florida, where Bubbles is living ''in retirement'', told National Enquirer magazine: ''Bubbles was not provided for in Michael Jackson's will''.
Michael's three children, Prince, 15, Paris, 14, and 10-year-old 'Blanket', used to play with Bubbles but have never been to visit their former friend at his new home.
Michael adopted Bubbles in 1983 and the pair formed a unique bond with the King of Pop often dressing the ape in the same outfit he was wearing. He would also be accompanied by his animal pal to awards ceremonies and showbiz events.
It was recently claimed the 'Billie Jean' singer was convinced his pet had an instinct for being able to tell who in his family was trying to live off his fortune.
Michael is said to have barred siblings from his Neverland ranch if the pet did not like them.
The late pop superstar reportedly told staff: ''He is a good judge of character''.
A former housekeeper said: ''Bubbles often would be a gauge for Michael to decide who should stay and go''.