Michael Jackson's former doctor has confessed he has previously donated sperm - but is unaware if it was used to father the singer's two oldest children.

Dr. Arnold Klein - who is rumoured to the biological dad of Prince Michael, 12, and 11-year-old Paris - once gave his semen to a sperm bank but insisted he never donated it to the late pop star.

Klein - whose former nurse Debbie Rowe was once married to Michael and is the mother of Prince and Paris - told US TV show 'Larry King Live': "I once donated sperm but it was absolutely not to him."

Having previously denied being the father of the children, when Klein was asked again who the biological dad was, he replied: "Here's the most important thing. Michael loved those children. Those children loved him as a father. As far as I am concerned, that's the most important grouping there is."

When pressed further, he replied: "I'm not going to answer it the way you want me to answer it because... I will say no if that's what you want to hear.

"What I will tell you is I think what's most important about this whole thing, about who the father is... is who the children want their father to be.

"I think, to the best of my knowledge, I'm not the father."

Although Michael - who went on to have another son, Prince Michael II, also known as 'Blanket', via a surrogate mother - always insisted he was Prince and Paris' biological father, Debbie previously alleged they were conceived using artificial insemination with sperm which was not Michael's.

Klein - who was the 'Thriller' singer's dermatologist for 20 years - also admitted he performed several cosmetic procedures on Michael, in particular his nose.

He said: "I rebuilt it, yes. Using fillers. I used Rezulin. I used hydronic acids, and they worked very well. It's an arduous procedure, because you don't want to put too much in. And you have to do it exactly, so you can flow the material so it's perfectly smooth.

"So we rebuilt them. And I'm telling you that he was beginning to look like the nose was normal again. And that's all I wanted - for him to regain the breathing in the passages of his nose, because there was a total collapse of the cartilage."

He also confessed to giving him Demerol, the powerful painkiller Michael was reportedly addicted to.

He claimed he only gave him the drug "on occasion" to sedate him and that it was the "strongest medicine" he'd ever administered to Michael - who died from a suspected cardiac arrest last month, amid allegations he was taking a cocktail of prescription drugs.