"This decision comes as a result of an ongoing review process, which initially included the announcement of a suspension. It also takes into account many conversations with our own employees," NBC News said in a statement.
The announcement also was made on air.
Imus triggered the uproar on his April 4 show when he referred to the mostly black Rutgers women's basketball team as "nappy-headed hos." His comments have been widely denounced by civil rights and women's groups.
CBS Radio issued a statement saying it is sticking to its decision to suspend "Imus in the Morning" for two weeks, reports CBS News correspondent Anthony Mason.
But Bruce Gordon, a director of CBS Corp., and the former head of the NAACP, said Wednesday the broadcasting company needs a "zero tolerance policy" on racism and that Imus should be fired for his remarks.
The program originates from New York radio station WFAN and is syndicated to other radio stations by CBS Radio. Both, like CBSNews.com, are part of CBS Corp.
"He's crossed the line, he's violated our community," Gordon said in a telephone interview with The Associated Press. "He needs to face the consequence of that violation."
Gordon, a longtime telecommunications executive, stepped down in March after 19 months as head of the National Association for the Advancement of Colored People, one of the foremost U.S. civil rights organizations.
He said he had spoken with CBS chief executive Leslie Moonves and hoped the company, after reviewing the situation, would "make the smart decision" by firing Imus rather than letting him return to the air at the end of a two-week suspension that was announced Tuesday.
A CBS spokesman, Dana McClintock, declined comment on the remarks by Gordon, who is one of at least two minorities on the 13-member board.
Rutgers women's basketball coach C. Vivian Stringer said Wednesday night she was surprised at MSNBC's announcement, but heartened that the public had reacted so strongly against his comments.
Stringer, though, said the firing would not change plans for the players to meet with Imus in the future to discuss the comments.
"At no time were we trying to make a decision about whether he should be hired or fired," Stringer said in a telephone interview.
MSNBC's decision to drop the simulcast came after a growing list of sponsors — including American Express Co., Staples Inc., Procter & Gamble Co., and General Motors Corp. — said they were pulling ads from Imus' show for the indefinite future.