Steamed up OPRAH WINFREY’s feud with ex-pal MICHELLE OBAMA explodes as the First Lady and pop star Beyonce  carry on a public love fest – AND Oprah is furious!

Michelle, 48, kissed up to new mom Beyonce, 30, during a recent interview on “Good Morning America,” adding more fuel to her long running feud with Oprah, sources say.

“At one time Oprah considered Michelle and her husband Barack as intimate friends, but a lot has changed in the past couple of years,” said an insider.

The talk-show queen, 58, knew the Obamas way back when he was the junior U.S. senator from Illinois and Michelle was a University of Chicago hospital administrator. They often socialized together, and when Barack announced his first White House run, Oprah immediately jumped on board his campaign wagon.

The billionaire media mogul endorsed her pal for president, and opened her glitzy estate in Montecito, Calif., for a celeb-studded Obama fundraiser. So when the Obamas moved into the White House, Oprah felt entitled to special treatment, sources say.

Instead, as The ENQUIRER reported in January 2010, Oprah was told that she had to go through Michelle’s assistants if she wanted to hook up with the first couple, sparking a huge feud between the two women. Their power struggle became so heated that President Obama was forced to step in and play peacemaker.

But his bid to soothe the troubled waters between the two women failed.

Now Oprah feels Michelle – who attended Beyonce’s first post-baby concert in Atlantic City on May 25 with daughters Malia, 13, and Sasha, 10 – has stirred the pot publicly with her recent remarks on “Good Morning America.” While promoting her new book “American Grown: the story of the White House Kitchen Garden and Gardens Across America,” Michelle gave a shout-out to Beyonce, saying: “I love her to death.”

Michelle also said that she admired the pop diva for supporting the first lady’s childhood anti-obesity campaign, Let’s Move!

“Oprah viewed Michelle’s comments as a personal dig at her for being overweight, as opposed to Beyonce who looks fabulous just weeks after giving birth,” added the insider.

 “Oprah was there for the Obamas when they were local politicians, and now that  they’ve become A-list celebs, she feels that she’s been pushed aside for Beyonce.

“While she’s already endorsed Barack, Oprah will NOT be out cheering for him on the campaign trail.

“She told a friend, ‘Let Beyonce do it! I’m DONE!”