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.