MICHELLE OBAMA is already hammering away at a $15 million memoir that will rip the lid off President Barack Obama’s secret extramarital hijinks and public flirta­tions with other women, sources tell The ENQUIRER.

“Michelle has suffered in silence, while Barack ignored her to live it up surrounded by adoring beauties,” an insider told The ENQUIRER.

“She’s fed up, and she’s going to use a poison-pen memoir of her White House years to get revenge on him.

“The book will be based on her diaries and tell the world about Barack’s flirting, drinking and hanging out with fawning women. Mi­chelle doesn’t want to come away as Hillary Clinton, who stood by her man Bill when he cheat­ed like a dog, but as a strong woman.” Another source added: “Michelle feels she’s been made a laughingstock on the world stage, and she plans to get her revenge with this memoir.

“Michelle knows this book will create tremendous problems for Barack. But she feels that after what he’s put her through, he deserves it.”

Michelle also plans to reveal she was once so angry she had divorce papers drawn up but decided for the sake of her husband’s presidency not to use them – yet.

Meanwhile, President Obama is expected to pocket up to $20 million for his memoirs after he leaves the Oval Office, while Michelle could see a $15 million payday, sources say.

But as Michelle prepares to put pen to paper, the couple’s 21-year marriage has exploded into all-out war, sources say.

“Barack asked Michelle to not start writing her book until AFTER his sec­ond term ends,” said the insider. “He told her she’d have a better perspective on things. But deep down, he knows that she’s been rip-roaring furious at him and he knows he’s going to come out looking really bad.”

Recently, Michelle read Barack the riot act because his drinking has been escalating – and then he had the audac­ity to declare that marijuana is no more dangerous than alcohol.

“She reminded him that the pot out there these days is a lot stronger than what he and his ‘Choom Gang’ pals smoked back in Hawaii,” said a source. “And she told him it was especially unforgiv­able considering they have two daughters who are at an age when they’ll be exposed to the temptations of experimenting with drugs”.

Meanwhile, as The ENQUIRER has re­ported, the first lady had been seething for months over her husband’s infatuation with “Scandal” star Kerry Washington, whom she once banned from the White House. Then Obama made international headlines by shamelessly flirting with Denmark’s dishy female prime minister at the late Nelson Mandela’s memorial service in South Africa in December.

The randy chief executive even posed for a “selfie” with leggy blonde Helle Thorning-Schmidt while Michelle shot him daggers.

The humiliating incident sparked a furious argument when the first cou­ple returned to Washington, D.C., and the fighting continued during their annual holiday vacation in Hawaii.

As we reported, the Hawaii trip went from bad to worse when Michelle was told that the Secret Service had been covering up her husband’s infidelities.

“Michelle learned that Barack was caught with a woman in an incident that, in the words of one mole, was ‘hushed up,’” said one source.

“Besides that, a Secret Service agent also saw the president ‘in a compromising posi­tion’ with another woman while Michelle was out of town.”

Afterward, the irate first lady ripped into her husband during a bitter blowout, raging: “I want out!”

Desperate to mend fences, Barack feted  Michelle with a celebrity-studded birthday bash in the White House’s East Room the night after she turned 50 on Jan. 17.

But sources say the birthday girl was still steaming over her husband’s ogling pro basketball star Dwyane Wade’s fiancée, actress Gabrielle Union, a few days earlier when the Miami Heat dropped by the White House to be honored for winning the 2013 NBA Championship. His lust was so obvious, one Internet site sniped that he’d eyed Gabrielle as if “she were the last hot dog at a cookout.” The Obama marriage took yet another punch to the gut when the British newspaper, “The Mail on Sunday,” reported on Feb. 1 that their union has been rocked by “screaming rows, allegations of infidelity and a string of jealous fights,” adding that the couple now sleep in separate bedrooms.

As The ENQUIRER has re­ported, the two seem headed for separate lives altogether. When Obama’s second term ends, he plans to live with his high school pal Bobby Titcomb, who was busted for solicit­ing a prostitute in 2011, in Hawaii.

Meanwhile, Michelle and their daughters Malia, 15, and Sasha, 12, will remain in Washington, D.C., until Sasha finishes high school.

“Michelle has also kicked Barack out of their house in Chicago, and as soon as his term is over, she plans to file for divorce,” the insider told The ENQUIRER.

“But she’s so furious that ending the marriage isn’t enough. In her memoir, she plans to write about the many times Barack humiliated her by throwing him­self at other women while she was just a few feet away – and she’s going to name names!”

In addition, sources say Michelle plans to get even with her perceived enemies, including the Clintons, Vice President Joe Biden and even the Kardashians, whom she feels dissed her for her fashion sense.

“She’ll write how Hillary used her Secre­tary of State position as a springboard for her own presidential aspirations and also how she and Bill were always just thinking about themselves,” said an insider.

“She also believes the Bidens gave her no respect, and she was incensed when one TV analyst called Jill the ‘best-looking campaigner in the race.’”

Michelle will also blast peo­ple who criticized her for her extravagant vacations that cost taxpayers millions.

“Michelle will write that the trips she took were deserved and that her critics should ‘get a life,’” said the source. “Af­ter all, she says that Nancy Reagan spent bundles in the White House, and no one criticized Jackie Kennedy for her trips to Europe.

“Michelle is definitely out for blood, but Barack will be the one who feels the full force of her fury!”