The 25-year-old reality TV star is reported to have split from the 'Shine Ya Light' singer today (03.12.12) and he has now taken to his twitter page to accuse the pop beauty of being unfaithful to him many times.
In now deleted messages on his twitter account, Rob angrily posted: ''She (Rita) cheated on me with nearly 20 dudes while we were together, I wonder how many she will sleep with now that we apart?
''But I mean 20?!!! 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?! (sic)''
Rob added: ''I'm actually disgusted a woman could give up her body to more than 20 dudes in less than a year's time while trying to start a career.''
The pair's separation had been blamed on Rita's hectic work schedule and their incompatible jet-setting lifestyles.
The 'Keeping Up with the Kardashians' star has also unfollowed the singer on twitter and deleted photos of them together on photo-based social networking site Instagram.
A source said: ''They'd only decided to go public with the romance a couple of months ago so as not to put any pressure on themselves but they've already split. Rob has now deleted everything on twitter that reminds him of Rita.''
There were signs of trouble between the pair when Rob skipped Rita's 22nd birthday party at London's DSTRKT nightclub last week.