Adele used to get so intoxicated before playing concerts that she once fell off a stool on stage.

The 'Rolling In The Deep' singer also forgot the words to one of her songs according to a new biography.

She described her memory lapse as "the worst thing ever", according to the book out next month.

The star's unofficial biographer Marc Shapiro told In Touch magazine: "Midway through her first tour, she allegedly had a drinking problem.

Apparently she told him in an interview: "I got so drunk by the time I went on at 2 am I had forgotten the words to my own songs ... It was the worst thing ever."

The author continued: "Adele would drink more than normal to salve the heartbreak."

According to his book Adele: The Biography, her bisexual boyfriend cheated on her, leaving the 24-year-old distraught.

He continued: "She loved the drama surrounding boys who treated her badly.

"She had a fairly good self-image and seemed to handle it okay on the surface, but I'm sure it bothered her on a deep, emotional level."

Mark has previously written the biographies of Justin Bieber and Harry Potter author JK Rowling.

(Bang Showbiz)