REPRESENTATIVES of Michael Jackson have denied that the controversial pop star is in failing health and needs a lung transplant, calling the claim a "complete fabrication".

Author Ian Halperin, who is writing an unauthorised biography on Jackson, said the 50-year-old is suffering from the rare genetic illness, Alpha-1 antitrypsin deficiency, as well as emphysema and gastrointestinal bleeding.

Halperin also claimed that the singer can barely speak and is 95 per cent blind in his left eye.

"He's had it for years, but it's gotten worse," Halperin told US In Touch magazine.

"He needs a lung transplant but may be too weak to go through with it...(But) it's the (gastrointestinal) bleeding that is the most problematic part. It could kill him."

But a spokesman for Jackson said the story was wrong."Concerning this author's allegations, we would hope in the future that legitimate media will not continue to be exploited by such an obvious attempt to promote this unauthorised biography," Jackson spokesman Dr Tohme Tohme said in a statement to media outlets.

"Mr Jackson is in fine health, and finalising negotiations with a major entertainment company and television network for both a world tour and a series of specials and appearances."

Jackson is one of the best-selling recording artists of all time but has in recent decades been dogged by scandal and speculation about his lifestyle.

He was tried and acquitted of child sex abuse charges in 2005.