NBC has told Donald J. Trump, the Republican presidential candidate and former star of “The Celebrity Apprentice” reality show, that he’s fired.

After Mr. Trump made inflammatory remarks about Mexican immigrants, NBC said in a statement Monday that it was ending its business relationship with the billionaire real estate and media mogul. During his June 16 announcement that he was running for president, Mr. Trump referred to immigrants as “rapists” and “murderers.”

Citing the “derogatory statements,” NBC said it would also no longer air the Miss USA and Miss Universe pageants, which were part of a venture between Mr. Trump and the network.

Mr. Trump had taken steps to distance himself from “The Celebrity Apprentice” while he pursued his presidential campaign because of the conflict it presented. NBC, which had renewed the program for another season, would not allow Mr. Trump to appear on the air while running for office because of concerns that other candidates could request equal airtime. But he could have come back — and NBC probably would have welcomed him back — if he had dropped his bid at any point.

But his comments on Mexico and immigration made his relationship with the network untenable, and he appears to have permanently lost NBC as a platform for “The Apprentice” or any other program.

Last week, Univision said it would no longer air Mr. Trump’s pageants after his remarks. Mr. Trump suggested that he might take legal action for breach of contract and banned Univision executives from using his golf course in Miami.

By Monday, a Change.org petition urging NBC to end its relationship with Mr. Trump had garnered more than 200,000 signatures, adding to pressure on the network to end the relationship.

The show was once a hit for NBC, but its viewership has waned in recent years. In its first season in 2004, it gave NBC a much-needed ratings boost when the show averaged almost 21 million viewers, according to Nielsen. But the most recent season of “The Celebrity Apprentice” brought in 7.6 million viewers an episode, an improvement over each of the previous two seasons but significantly lower than in the first five seasons. The most recent season, which ended in February, was the first “Celebrity Apprentice” season since 2013.

Nevertheless, NBC said it would move forward with the show. It said the show was “licensed from Mark Burnett’s United Artists Media Group, and that relationship will continue.” The network did not say who would replace Mr. Trump as host.

Also Monday, Ora TV, a production company co-founded by the Mexican billionaire Carlos Slim Helú and the TV personality Larry King, canceled a program it was working on with some of Mr. Trump’s companies, Reuters reported.

Mr. Trump has brushed off criticism over his comments and has said his wealth gives him the ability to speak his mind freely without worrying about political backlash or the need to please donors. He said in an interview with CNN over the weekend that he was forgoing millions of dollars in business opportunities to pursue his run for president.

With the loss of his NBC platform, Mr. Trump’s presidential bid became more personally costly. However, at a news conference Monday in Chicago, he stood by his immigration comments and said NBC had been unhappy with him since he decided to run for president and step away from his show.

“I told NBC I could not change my stance,” Mr. Trump said, suggesting the network could face a lawsuit for violating their contract. “The fact is that my stance on immigration is correct.” Mr. Trump also derided the company over its handling of Brian Williams, the news anchor who was demoted after embellishing his reporting experiences.

“They will stand behind lying Brian Williams, but won’t stand behind people that tell it like it is, as unpleasant as that may be,” Mr. Trump said.