Rihanna is reportedly to blame for Rita Ora's decision to sue their record label Roc Nation as she's said to have used her influence to ensure her rival's career was not treated as a priority. The 'Body On Me' singer is said to have taken the label to court in a bid to get herself released from her contract with them after Rihanna - who is also signed to Roc Nation - used her influence to make sure her rival's career was not treated as a priority. A source said: ''Rihanna has never liked Rita and has been using her power at Roc Nation accordingly. ''This is the main reason the label's execs have been uninterested in putting effort into promoting Rita. ''Songs that might be submitted to her are automatically given to Rihanna, who may then hold them for months before deciding she doesn't want them.'' However, Rita's plans to leave the label are also said to have been caused by her split from 'Summer' DJ Calvin Harris - who is now dating Taylor Swift. The insider told The Sun newspaper: ''The fact that Rita's ex Calvin Harris is on their management books hasn't helped either. He is one of their highest earners and they did nothing to stop him when he blocked Rita from using songs that he had written on her album.'' In papers filed to Los Angeles' Superior Court last week Rita described her relationship with Roc Nation as ''irrevocably damaged''. Meanwhile, this is not the first time news of Rita and Rihanna's rivalry has emerged as the 'Diamonds' singer banned Rita from attending her Met Gala after-party earlier this year. And Rihanna is also said to have been furious at Rita for teaming up with her ex-boyfriend Chris Brown - who was arrested in 2009 for assaulting her - on the single 'Body On Me'...