Michael Jackson’s dermatologist Dr. Arnold Klein is planning to appeal a judge's decision to ban him from playing an official role in the lives of the superstar's children.

The skin doctor's lawyer, Mark Vincent Kaplan, stunned onlookers at Los Angeles County Superior Court on Monday when he asked for Klein to be considered in the guardianship case involving Jackson's eldest children, Prince Michael, 12, and Paris, 11.

Klein claims he made the petition because he once promised the late King of Pop he would look after his kids.

Judge Mitchell Beckloff rejected the bid and ruled the medic had no legal standing in the children's lives, before naming Jackson's mother Katherine as the permanent guardian of Prince and Paris, as well as their seven-year-old brother Prince Michael II, aka Blanket.

But Kaplan reveals his client is refusing to drop the case and he has been instructed to file an appeal in September.

He tells TMZ.com, "We're gonna file something... We agreed that we would not file it before September."

Katherine Jackson was handed custody of her three grandchildren after reaching a settlement with the Thriller hitmaker's ex-wife Deborah Rowe, the biological mother of the star's two eldest kids. Prince Michael II was delivered via a surrogate, whose identity has not been revealed.

Reports suggest Klein is the biological father of Jackson's eldest children.