Bruce Jenner
Bruce Jenner is reportedly transitioning into a woman.Getty

Hollywood actor Jamie Foxx has been accused of transphobia after making a joke about Bruce Jenner's alleged sex change at the 2015 iHeartRadio Music Awards.

The 47-year-old star, who was hosting the event held at LA's Shrine Auditorium, appeared to mock the reality star during the opening segment of the show.

Taking to the stage following a performance from Jennifer Hudson and Iggy Azalea, he said: "We have some ground-breaking performances here too tonight. We got Bruce Jenner, who will be here doing some musical performances. He's doing a his and her duet all by himself."

Foxx added: "Look, I'm just busting your balls while I still can."

But the gaffe didn't go down well with the audience - a crowd that was expected to include Jenner's daughter Kylie Jenner - with the backlash spilling onto social media.

Openly gay celebrity blogger Pezez Hilton was first to tweet, lambasting Foxx for his comments.

Other Twitter users also shared Hilton's sentiments.

Jenner has been the focus of sex-change rumours after he reportedly had his Adam's apple surgically reduced, a common procedure by men seeking gender reassignment. He also allegedly started taking oestrogen and asked to be referred to as "Brigitte".

Although, the 65-year-old star has not publicly addressed the transition rumours, People Magazine previously reported that he became aware in his early teens of his desire to dress as a woman, he spent almost 50 years in denial.

It also claimed that the 65-year-old's stepdaughters struggled to come to terms with his decision and that he is no longer on speaking terms with ex-wife Kris.

"They were just hysterical when it all really came out," a source said of Kim, Kourtney and Khloe, who were the last to find out Bruce was making the change.

The insider added: "The divorce caused a divide, but Bruce's decision to share his transition has caused an even greater divide."