Reality star Rob Kardashian has admitted that he attempted to ruin Rita Ora's reputation after she ended their year-long romance.

Kim's Kardashian's young brother made headlines in 2012 when he publicly accused his former lover of cheating on him with 20 other men while they were still in a relationship.

In a string of hostile tweets after the break-up he told his 3.8 million followers: "She cheated on me with 20 dudes while we were together. I wonder how many she will sleep with now that we're apart. I mean 20?#

He later added: "How can a woman who is so busy trying to start her own career have time to be with so many dudes all while in a relationship?

"I'm disgusted a woman could give up her body to more than 20 dudes in less than a year while trying to start a career."

Minutes after he posted his rant #RitaWhora became a top trending topic on Twitter and rumours began to circulate about the RIP hitmaker's personal life.

But in an upcoming episode of Kourtney & Kim Take Miami, 25-year-old Rob confesses he made up the claims about Ora because he was angry.

"I posted what I posted to keep myself from taking her back," he said. "Every time she messed up, I took her back. I just had to do that to make her hate me," he says.

"I don't want people to think I'm being a bitch."

Ora is believed to have called things off with the Keeping up with the Kardashians star because of her hectic work schedule and the long distance between them.