The tycoon is understood to have walked away from the singer as she prepares to expose much of her glittering life on a new reality TV show, allowing her to keep the $10m diamond engagement ring he gave her in January.
“It’s all over,” confirms one close family friend.
“James had huge reservations about Mariah’s new reality TV show and the fact that she was willing to expose their lives to the world.”
The news comes as no great shock to friends and relatives of the Packer family who have had reservations about the relationship ever since James started wooing the flamboyant singer in Las Vegas last year.
WATCH: The trailer for Mariah’s World. Post continues after the video...
Mariah, 46, created tension within the family after refusing to attend James’s sister Gretel’s 50th birthday in Sydney earlier this year, and his mother, society matriarch Ros Packer, struggled to connect with the singer.
There have rumours for weeks that the glamour couple were experiencing difficulties, particularly as Mariah devoted much of her time to a reality TV show about her life, which James, 49, was reluctant to participate in.
The couple have spent hardly any time together in recent months amid increasing concerns among his friends about her lavish lifestyle and over the top spending sprees. “James is very generous but Mariah takes it to the next level,” reveals one close friend.
“When she refused to come to Australia for Gretel’s birthday party it created a lot of tension in the family. His mum hated to even hear her name mentioned, and James’ tight circle of friends never really thought they would marry.”
James has turned to his first wife, fashion designer Jodhi Meares for support since splitting with Mariah, who has been spending time with her ex-husband, Nick Cannon.
Mariah has previously praised her fiance’s generosity, saying they “fell head over heels in love with one another” after meeting after one of her Las Vegas shows. James has long been a fan of Mariah’s music.
"As soon as their friendship turned romantic, they have wanted to spend every moment together," one source revealed earlier this year.
"They have a connection that is unparalleled; it's been a very beautiful experience for them both. If you spend even five minutes with them, you can't help but believe in true love."
But in recent months the couple were increasingly at loggerheads over Mariah’s new reality TV show, which threatened to expose much of the notoriously private James’ lifestyle.
Meanwhile prompting further speculation something is up in Mimi's camp, the singer has cancelled her upcoming tour dates in Brazil, Argentina and Chile.
"To all of my lambs in South America, I am devastated that a portion of this tour had to be cancelled. Thank you for all of the excitement and love - I hope to see you soon, my darlings," the star said in a statement to E! News.