The superstar’s marriage has once again been in the headlines as Becoming Beyonce: The Untold Story hits the shelves

Beyonce and Jay Z have long been plagued by cheating rumours, but according to the author behind a new unofficial biography – the singer would LEAVE her husband if she found out he did stray.

J Randy Taraborrelli’ s Becoming Beyonce: The Untold Story has revealed a shocking look into the life of the very private superstar and her marriage to hip-hop mogul Jay Z.

The 45-year-old has been linked to a string of women while married to the Drunk In Love star – including his own artists Rihanna and Rita Ora – but author Taraborrelli doesn’t believe the rapper would cheat because Beyonce would almost certainly end their marriage.

Jay Z and Beyonce at the Met Gala 2015

“One thing I’ve learnt from spending two years looking at Bey’s life is that if you think she’s that girl who’s going to sit on the sidelines and watch her husband cheat, then you are very wrong,” he told Heat Magazine.

“She has other issues, as we all do, but she isn’t wiling to accept the unfaithfulness of a spouse. She’s been very clear with Jay: ‘If you cheat on me, it’s over.'”

The main speculation surrounding an extra-marital affair centres on Rihanna – who as a 17-year-old was discovered by the Watch The Throne star.

Rihanna and Beyonce pose backstage at the adidas Originals x Kanye West fashion show

At the time it didn’t take long before allegations about a romance surfaced.

According to Becoming Beyonce though, Jay was completely innocent and the rumours were actually started by Jonathan Hay.

Hay said in an interview that he’d been an early publicist for the star and had started the rumours in an attempt to stir up some interest in the teenage singer.

Lawyers for Rihanna have dispute Hay’s claims, insisted he never worked for her and has never met the Bajan singer.

Last week he revealed he’d apologised to Beyonce for fabricating the rumours, in a bid to boost Rihanna’s profile.

Jay Z and Rihanna have been long time collaborators

Speaking to the New York Daily news, Hay said: “I apologised to her… this whole thing is very awkward.”

He added to Inside Edition: “I was desperate at the time because I wanted to have a hit record. We were young and stupid.”