Paramount believes, according to this person, that Plan B violated its deal with the studio by not offering it a chance to distribute the picture, which was released in October.
New Regency declined to comment about the "12 Years a Slave" matter. Plan B did not immediately respond to a request for comment.
It has been a busy few days for Paramount, which has lost one top-tier producer, but gained another. On Dec. 6, the studio announced it had inked a first-look deal with producer Jerry Bruckheimer.
As part of that three-year pact, Bruckheimer will produce "Top Gun 2" and a "Beverly Hills Cop" picture for the studio.
Plan B's deal with New Regency and RatPac is the last company's second high-profile film financing accord in recent months.
RatPac's Ratner directed the "Rush Hour" trilogy and is making "Hercules: The Thracian Wars" for Metro-Goldwyn-Mayer Pictures and Paramount. Packer is the chairman of Crown Ltd., a hospitality and entertainment company based in Melbourne.
“Plan B has become a consistent supplier of top-tier material and talent. As a new company, for us to be able to partner with Arnon and his team at New Regency on this deal, it gives us a great jump-start for what we are trying to accomplish,” Packer and Ratner said in a statement.
Plan B's impending departure from Paramount was first reported Tuesday by the Hollywood Reporter.
Staff writer John Horn contributed to this report.