JACKIE KENNEDY’s BFF singer CARLY SIMON’s tell-all rips the lid off CAROLINE’s feud with mom and MORE in tell-all!

JACKIE KENNEDY hated daughter Caroline Kennedy’s husband Ed Schlossberg and called him a “boring old fogey” and an “egghead” behind his back!

And she only accepted their rela­tionship after Caroline threatened to elope and to keep her from seeing her future grandchildren.

That’s just one of the shocking secrets Jackie’s good pal, Grammy win­ner Carly Simon, 67, plans to divulge in an explosive new autobiography planned for release next year.

“Carly has lived an outrageous life and knows some of the hottest, best-kept secrets of the rich and famous,” a publishing insider told The ENQUIRER.

While the “You’re So Vain” singer will “drop bombshell after bombshell” in the book about her celebrity lovers and emotional divorce from singer James Taylor, it’s the secrets from the former first lady that will prove the most eye-opening, says the insider.

The two women met as neighbors on Martha’s Vineyard in 1978, and “few people realize that Carly was one of Jackie O’s closest confidantes” during that time.

According to the book, which will be published by Random House, “Jackie desperately hoped Caroline, now 54, would grow tired of her older suitor Schlossberg, now 66, during their courtship. “And she was horri­fied when Caroline announced she was going to marry him.

“Caroline finally told Jackie, ‘I’m marrying him, like it or not. You don’t even have to be there. But you won’t see your grandchildren if you don’t accept their father.’

“Jackie begrudgingly accepted Ed, but privately she called him a boring old fogey and an egghead!”

Carly also plans to share her strug­gles with marijuana and prescription painkillers as well as the divorce from Taylor, who had his own drug prob­lems.

“This is the first time in her life that she wants to publicly face the demons that have plagued her,” added the insider.