A biography on Adele claims the singer had a terrible drinking problem and adds that the popular singer lost her bisexual boyfriend to his gay best friend.

One claim from the book is that 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 the new biography.

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

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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.

(Image: WENN)