Michael Jackson is said to be so frail he can barely speak. (Sun Media file photo)

Michael Jackson is battling a genetic disease that has left him half blind and needing a lung transplant, London's Sun newspaper is reporting.

The 50-year-old Jackson is said to be so frail he can barely speak.

“He needs a lung transplant, but may be too weak to go through with it. He also has emphysema and chronic gastrointestinal bleeding, which his doctors have had a lot of trouble stopping," Jackson’s biographer, Ian Halperin, told London's Sun.

“It’s the bleeding that’s the most problematic part. It could kill him.”

Halperin, an award-winning investigative journalist from Montreal, said Jackson was stricken with an inherited condition called A1AD — alpha-1 anti-trypsin deficiency. Sufferers lack a protein which protects the lungs.

The biographer, who has written for Rolling Stone magazine, said Jackson “can barely speak. The vision in his left eye is 95% gone."

According to the Sun report, Jackson’s brother Jermaine confirmed, saying: “He’s not doing so well right now. This isn’t a good time.”

Fox News, meanwhile, is reporting that Jackson insiders say the reports of his ailing health have been extremely exaggerated.

The headline on the Fox News report says it all: "Jacko Not Sick, Except In Head."

Jackson has not yet responded to either of the reports.