The 'Anywhere' singer has left Next Model Management after six years and has decided to join Kate Moss Agency, the rival company founded by supermodel Moss in 2016.
Speaking to The Sun, Rita - who previously hosted 'America's Next Top Model' - said: ''Kate has always been a mentor and life-long friend. It's a real honour to be working with her.
''I have watched her career and business grow, and establish itself as one of the most important and recognisable brands.
''She is a real inspiration, and when we discussed going in to business together, it seemed natural.''
It has been claimed that Rita's split from Next was acrimonious and she had a ''difficult working relationship'' with the agency.
An insider told the paper: ''This is a great career move for Rita and is sure to bring in loads more work for her. But it hasn't come from the best situation.
''Things with Next weren't great and they really weren't too disappointed about her moving on, because it was a difficult working relationship.''
Along with developing her career as a model, singer Rita, 27, recently insisted she wants more acting roles.
The star has appeared in the 'Fifty Shades' trilogy and Jake Gyllenhaal's 'Southpaw' and hopes to take on leading roles of her own in the near future.
She said: ''I would definitely have to wait and see what roles I get offered. It's all based on that. But yes, definitely something I would love to do more in the future.''