NEW YORK (AP) _ CBS-Fox Co. has charged in a $50 million lawsuit that MGM-UA Communications Co. violated an agreement that gives CBS-Fox the right to distribute MGM-UA movies on videocassette.

The lawsuit stems from the settlement of an earlier dispute that called for the home video rights of each movie released by MGM-UA to be split alternately between CBS-Fox and MGM-UA's own video distribution company.

CBS-Fox claims that MGM-UA reneged on the agreement by manipulating the release date of movies to deny CBS-Fox successful and lucrative films like ''Poltergeist II'' and ''Running Scared.''

The lawsuit, which was filed Wednesday in U.S. District Court in Manhattan, seeks $50 million in damages from MGM-UA.

''We're not happy with the deal,'' said James Lopes, a spokesman for CBS- Fox in New York. He declined to comment further on the litigation.

A call to William Jones, the general counsel for MGM-UA, was not immediately returned.

CBS-Fox, which is owned jointly by 20th Century-Fox Video Inc. and CBS Inc., distributes movies for home viewing. It entered into an agreement in 1981 with United Artists to distribute all its movies.

Shortly thereafter, UA was acquired by Metro-Goldwyn-Mayer Film Co., which had its own videocassette distribution house.

CBS-Fox first sued MGM-UA in 1983, claiming the merger resulted in a violation of its original contract with UA. That lawsuit resulted in the agreement which CBS-Fox now claims MGM-UA is not following.