MSNBC has parted ways with host Melissa Harris-Perry after she complained about preemptions of her weekend program and implied that there was a racial aspect to the cable-news network’s treatment, insiders at MSNBC said.

Harris-Perry refused to appear on her program Saturday morning, telling her co-workers in an email that she felt “worthless” to the NBC-owned network. “I will not be used as a tool for their purposes,” wrote Harris-Perry, who is African American. “I am not a token, mammy or little brown bobble head. I am not owned by [NBC executives] or MSNBC. I love our show. I want it back.”

The rebuke, which became public when it was obtained by the New York Times, has triggered discussions involving the network, Harris-Perry and her representatives about the terms of her departure, said people at MSNBC, who spoke on the condition of anonymity because Harris-Perry’s departure has not been formally announced.

The flap with Harris-Perry, who did not respond to a request for comment, follows a strategic transformation of MSNBC that has swept up several of its minority program hosts. Specifically, the network — which typically finishes far behind Fox News and CNN in cable-news ratings — has been trying to emphasize breaking-news coverage during daytime hours while maintaining a slate of liberal hosts during prime-time hours at night. Like its competitors, it has emphasized breaking campaign coverage, which lately has bumped Harris-Perry from her regular spot.

The network earlier faced some outcry on social media over its irregular preemptions of Jose Diaz-Balart, who hosts a two-hour bloc from 9 to 11 a.m. weekdays. Diaz-Balart’s disappearance from the air prompted a hashtag — #MasJose — and a petition to encourage MSNBC to feature him on the air more often.

Diaz-Balart’s hosting duties are also in question at the network. Scenarios under review include extending the “Morning Joe” program into Diaz-Balart’s slot or creating a new program hosted by one of “Morning Joe’s” regular personalities. Diaz-Balart, who also anchors for NBC-owned Telemundo, is based in Miami, which complicates his role anchoring weekday coverage for New York-based MSNBC. He will continue anchoring “NBC Nightly News” on Saturdays.

All of the changes carry a potential perception risk that MSNBC — known as the most liberal among the three leading cable-news networks — is diminishing the contributions of its minority personalities, network officials acknowledge. In addition to the issues with Harris-Perry and Diaz-Balart, the network’s new emphasis on news during the day has led to the demotion of two African American hosts: the Rev. Al Sharpton and Joy Reid, both of whom have been moved from daily shows to lower-profile weekend slots. (Reid assumed Harris-Perry’s hosting duties on Saturday.)

At the same time, the network brought back Brian Williams to be its leading daytime news anchor. Williams was suspended by NBC and ultimately lost his job as the anchor of NBC’s “Nightly News with Brian Williams” last year after he exaggerated the details of his reporting exploits in a series of media appearances.

In a statement, MSNBC spokesman Mark Kornblau said: “We are proud of the diverse backgrounds and viewpoints of our journalists, opinion hosts and analysts. We will gladly put that up against everyone else in the news business.”

MSNBC’s pivot to more news reporting, especially campaign coverage, has lately resulted in improved ratings. So far this year, its weekday ratings among all viewers have grown 57 percent over the same period in 2015, compared with a 38 percent gain for CNN and 20 percent for Fox News, the cable-news leader, according to MSNBC. Among viewers aged 25 to 54, a key bloc for advertisers, MSNBC is up 76 percent, compared with 25 percent for CNN and 19 percent for Fox.

MSNBC executives said that they were surprised by Harris-Perry’s blast on Friday and that it may have stemmed from her perception — incorrect at the time, but now a reality — that her weekend program was about to be canceled. “She’s a brilliant, intelligent but challenging and unpredictable personality,” one executive said. “There was no plan to cancel her.”

He added, “It’s highly unlikely she will continue” at MSNBC. Her email “is destructive to our relationship.”

This executive disputed Harris-Perry’s assertion that MSNBC executives had not communicated with her, although he said Harris-Perry has never met Andrew Lack, the NBC News chairman who was rehired by the network last year after the controversy over Williams. The decision to preempt Harris-Perry’s program for election-news coverage over the past several months was made by Phil Griffin, MSNBC’s president.

Harris-Perry, a professor at Wake Forest University, joined MSNBC four years ago at a time when the network was attempting to graft its opinionated evening programs onto its daytime schedule. While such evening hosts as Chris Matthews, Chris Hayes and Rachel Maddow have proven relatively popular, the liberal-talk format was unsuccessful during the lighter-viewed daytime hours.

In her email to her colleagues, Harris-Perry wrote, “Here is the reality: Our show was taken — without comment or discussion or notice — in the midst of an election season. After four years of building an audience, developing a brand and developing trust with our viewers, we were effectively and utterly silenced.”

In a follow-up phone interview with the Times, Harris-Perry softened the racial aspects of her criticism, saying: “I don’t know if there is a personal racial component. I don’t think anyone is doing something mean to me because I’m a black person.”