Michael Jackson

But the ailing star is too weak to be rushed into surgery and may even be fighting for his life, claims Ian Halperin, a former award-winning investigative journalist on America's respected Rolling Stone Magazine. Canadian Halperin says Jackson, 50, has been diagnosed with Alpha 1-antitrypsin deficiency, a genetic condition that can be fatal in severe cases. And he claims the singer is now so ill he can barely speak and has lost as much as 95 per cent of the vision in his left eye. Jackson was photographed in Los Angeles ten days ago visiting a doctor prior to shopping in several of his favourite stores with aides. The singer, who wore a Long Ranger style mask and Indiana Jones fedora to almost completely hide his face, was able to walk unaided, despite being seen in a wheelchair earlier this year near his home in Las Vegas.

Jackson's condition has worsened to the point where his quality of life is severely diminished

But Halperin claims Jackson's lung condition has become more acute, causing the spin-off pulmonary disease emphysema often associated with heavy smokers – even though he has never touched cigarettes. The writer added: "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."

Jackson's official spokeswoman would not comment on Halperin's claims but Jackson's older brother Jermaine seemed to confirm that the singer has serious health issues.He told America's Fox TV news: "He's not doing so well right now. This isn't a good time." Author Halperin added that Jackson's lung conditions – which affects only one in 5,000 Americans – has been difficult to treat because of the 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 stabilized him."

But as the disease has progressed, Halperin added, Jackson's condition has worsened to the point where his quality of life is severely diminished. The author said: "He can barely speak. Also, the vision in his left eye is 95 per cent gone." Marlene Erven, executive director of the American Alpha-1 Association, which represents sufferers, said: "This is a rare disorder. There is a protein deficiency that prevents the lungs from being properly protected during the everyday act of breathing. Patients often develop emphysema and either lung or liver disease, which can be fatal."

Jackson, whose attorneys revealed he had become dependent on morphine and the potent painkiller Demerol prior to his California trial in 2005 when he was cleared of child molestation, has long been beset by health problems. Despite flickering hopes of a professional comeback following a self-imposed period of exile in Bahrain, the singer now rarely leaves his rented mansion in Las Vegas. He was unable to attend a hearing last month at the High Court in London where Bahrainian prince, Sheikh Abdullah was suing him for allegedly failing to honour a $7 million business deal. Jackson, who settled out of court with the prince, revealed earlier this month that he plans to sell off thousands of items of personal memorabilia at a five-day auction beginning on April 21 in Beverly Hills.