In an unusually public flare-up, one of MSNBC’s television personalities clashed with the network on Friday in a dispute about airtime and editorial freedom and said she was refusing to host the show that bears her name this weekend.

The host, Melissa Harris-Perry, wrote in an email to co-workers this week that her show had effectively been taken away from her and that she felt “worthless” in the eyes of NBC News executives, who are restructuring MSNBC.

“Here is the reality: Our show was taken — without comment or discussion or notice — in the midst of an election season,” she wrote in the email, which became public on Friday. “After four years of building an audience, developing a brand and developing trust with our viewers, we were effectively and utterly silenced.”

In a phone interview, Ms. Harris-Perry confirmed she would not appear on the show this weekend. She said she had received no word about whether her show, which runs from 10 a.m. to noon on Saturdays and Sundays, had been canceled, but said she was frustrated that her time slot had faced pre-emptions for coverage of the presidential election. She said she had not appeared on the network at all “for weeks” and that she was mostly sidelined during recent election coverage in South Carolina and New Hampshire. (She was asked to return this weekend.)

In her email, Ms. Harris-Perry wrote that she was not sure if the NBC News chairman, Andrew Lack, or Phil Griffin, the MSNBC president, were involved in the way her show was handled recently, but she directed blame toward both.

“I will not be used as a tool for their purposes,” she wrote. “I am not a token, mammy or little brown bobble head. I am not owned by Lack, Griffin or MSNBC. I love our show. I want it back.”

Ms. Harris-Perry is black, and Mr. Lack and Mr. Griffin are white. In the phone interview on Friday, Ms. Harris-Perry clarified her remarks and said she did not think race played a role in her recent absence from the air.

“I don’t know if there is a personal racial component,” she said. “I don’t think anyone is doing something mean to me because I’m a black person.”

An NBC News spokesman said in a statement, “In this exciting and unpredictable presidential primary season, many of our daytime programs have been temporarily upended by breaking political coverage, including M.H.P. This reaction is really surprising, confusing and disappointing.”

For MSNBC, this is unwelcome news during a heated election. Last year, after its scandal involving Brian Williams, Mr. Lack, the former head of NBC News, was brought back to run the news division, and one of his chief missions was to fix the ailing MSNBC, which significantly trails Fox News and CNN in viewership. In last few months, Mr. Lack has steered MSNBC away from its liberal identity and moved it toward harder news in the daytime hours. Since January, the network has had round-the-clock election coverage (including the reintroduction of Mr. Williams as co-anchor on primary nights), and notched strong ratings gains year-over-year in the mornings and afternoon.

Ms. Harris-Perry, who is also a professor at Wake Forest University, has hosted her MSNBC show since 2012. She has used the show to explore issues like social justice and racism, and diversity has been the centerpiece of the show since its start.

Melissa is the best! I’ve been missing her show the last few weeks, and I can’t watch this endless primary coverage, especially the constant..

“I care only about substantive, meaningful and autonomous work,” she wrote in her email. “When we can do that, I will return — not a moment earlier.”

She said that last month the onscreen branding for her show was replaced by MSNBC’s slogan, “The Place for Politics.” With the election heating up, her show was pre-empted each of the last two weeks and for the most recent edition, on Super Bowl Sunday, she was told to talk mostly about the presidential race.

She still did speak about other topics, including Beyoncé’s new video for her song “Formation” and how it addressed race. But perhaps in a sign of the network’s shifting priorities, as she and her guests engaged in a lengthy discussion about the video, live video of rallies for Jeb Bush and Chris Christie in New Hampshire played in a box on the screen as well.

Ms. Harris-Perry, who is under contract, said that she was told that pre-emptions and election coverage were going to play out for the “foreseeable future.” Joy Reid will take over her time slot on Saturday, just as she has for the last couple of weeks.

Ms. Harris-Perry said not being able to talk to her viewers felt like a “betrayal.”

“It is perfectly fine, 100 percent reasonable and perfectly acceptable for MSNBC to decide they no longer want the M.H.P. show,” she said. “But they should say that. They should cancel the show; they should stand up. And maybe it would be rewarded with huge ratings, but they shouldn’t kill us by attrition and take us off the air without telling anybody, including us. That for me is what’s painful and difficult.”