The author behind a new biography of Michael Jackson has sparked rumours the star is seriously ill - suggesting the singer may be suffering from a deadly lung condition.

Ian Halperin, a former writer for America's Rolling Stone magazine, is producing a new book about Jackson's life and has detailed the Thriller hitmaker's medical problems - claiming he is suffering from a condition known as Alpha-1 antitrypsin deficiency, a potentially fatal genetic illness.

Halperin states that Jackson is losing the vision in his left eye and has subsequently developed emphysema, a lung condition linked to heavy smokers, which can be caused by the initial illness.

Halperin writes, "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. He can barely speak, the vision in his left eye has 95 per cent.

"For years Michael has been working with doctors to make sure it doesn't progress. He has been on medications that have stabilised him."

Jackson's older brother, Jermaine, recently hinted at the star's poor health, telling Fox News, "He's not doing so well right now. This isn't a good time."