Michael Jackson is reportedly close to death and urgently needs a lung transplant.

According to author Ian Halperin, the singer has been diagnosed with alpha 1-antitrypsin deficiency, a genetic condition that can be fatal in severe cases.

Investigative journalist Halperin, who is currently writing a biography on the troubled star, said Jacko needs an emergency operation but is too weak to be taken into surgery.

He told the Sunday Express newspaper that the 50-year-old singer is so ill he can barely speak and has lost 95 per cent of the vision in his left eye.

He said: "He has had alpha 1-antitrypsin deficiency for years but it's gotten worse. 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.

"It's the bleeding that's the most problematic part. It could kill him."

Halperin added that Jacko's lung condition, which affects only one in 5,000 Americans, has been difficult to treat due to its associated health problems.

He said: "For years, Michael has been working with his own doctors to try to make sure it doesn't progress. He has been on many medications that have stabilised him."

Although Jackson's spokeswoman wouldn't confirm Halperin's claims, the star's older brother Jermaine told Fox News: "He is not doing so well right now. This isn't a good time."