A parent's worst nightmare...

Amy Winehouse's father is voicing his worst fear: That his hard-partying daughter could die a "slow and painful death" from lung disease.

According to the BBC, Mitch Winehouse told the U.K.'s Sky News in an interview: "My biggest fear is that she would die," he said, "but she won't die of a drug overdose. It won't be that quick. She would die, unfortunately, of emphysema ... We would be talking about a very slow and painful death, gasping for air."

Even one more cigarette puts Amy's health in jeopardy, he told Sky, reminding viewers that doctors found "a small amount of emphysema in the top of one of her lungs," which could grow "a lot more serious."

That is why, he said, the "Rehab" singer will take a performing hiatus after September 6, when she's fulfilled her five remaining contractual gigs. From that date on, she'll be "relaxing and writing," Mitch told Sky, according to the BBC.

Earlier this week, the troubled star reportedly slapped a fellow patron at a London pub.