LISA MARIE PRESLEY and her husband Michael Lockwood are fighting so bitterly over her floundering music career that their marriage is on the brink of collapse, friends fear.

The only daughter of Elvis Presley has hit an exceptionally rough patch lately. Her recent 11-city concert series

was poorly attended, her latest album crashed and burned, and she feuded so bitterly with her tour manager that he quit!

“After the tour manager hit the road, all of those duties fell on Michael’s shoulders, which triggered

a lot of resentment and fights,” a source told The ENQUIRER.

“Their marriage was already struggling because the tour wasn’t going nearly as well as they hoped, in part due to Lisa Marie having some recurring health issues with her throat. The day-to-day stress really got to them, and they’ve been arguing ever since.”

Michael, 51, Lisa Marie’s fourth husband and the lead guitarist in her band, is also jealous of her first husband, Danny Keough, say sources.

Lisa Marie and Danny married in 1988 and have two children together, actress/model Riley, 23, and musician Benjamin, 19.

“Danny still plays a huge role in Lisa Marie’s life because of their children,” another source revealed. “But Danny’s presence is making Michael insecure about his relationship with Lisa Marie. He feels like Danny

needs to do his part to help with the kids, but he’d like for Lisa Marie to draw some firmer boundaries when it comes to their relationship.”

Meanwhile, Lisa Marie’s career continues to sputter. Her latest album, “storm & Grace,” has sold a measly 15,000 copies. it topped out at a lowly 45 ranking on the Billboard 200 after its release in May and fell off the charts altogether within a month.

Making matters worse, the flop album and failed concert tour came on the heels of what sources call a financial

disaster that the 44-year-old singer has been trying to keep under wraps.

“Lisa Marie is still reeling from the discovery that some of her most trusted handlers were taking money from her,” the first source noted.

“She won’t say how much money was lost, only that she’s badly embarrassed that it was happening right under her nose for a long time.

“After suffering such a huge financial hit, the last thing their marriage needed was a failed tour and low album sales.

The couple is currently preparing to kick off another concert tour in England, but the source said: “it will be a miracle if they can get through that without throwing in the towel.”