The BBC said on Monday that it would stop working with Gregg Wallace, a mainstay of the network and the longtime host of its hit television show “MasterChef,” after an investigation substantiated dozens of sexual misconduct allegations against him.

Of the 83 allegations made against Mr. Wallace, 45 were upheld, the broadcaster said. These included three instances of him being “in a state of undress” and one of unwelcome physical contact. The majority of claims against Mr. Wallace, who hosted the show for 19 years, involve “inappropriate sexual language and humor,” but the probe also found allegations of culturally and racially insensitive comments.

The investigation, conducted by the law firm Lewis Silkin, involved interviews with 78 witnesses over seven months. It covered incidents between 2005 and 2024.

“The volume and consistency of substantiated allegations” made Mr. Wallace’s return to the hit cooking show “untenable,” according to a statement from the production company behind the show, Banijay.

Mr. Wallace denied many of the allegations in a statement posted to Instagram. On Monday, he wrote, “I am deeply sorry for any distress caused.” He also said that “some of his humor and language missed the mark,” adding, “A late autism diagnosis has helped me understand how I communicate and how I’m perceived. I’m still learning.”

In a different statement posted on Instagram last week that was deleted on Monday, he wrote that he had been hired as the “cheeky greengrocer” — a role that included his warmth and rough edges. “Now,” he said, “in a sanitized world, that same personality is seen as a problem.”

Banijay ordered the investigation in December after the BBC reported that multiple women had accused Mr. Wallace of inappropriate conduct. Most of the complaints against Mr. Wallace, 60, occurred between 2005 and 2018.

The BBC said in a statement that Mr. Wallace’s behavior “falls below the values of the BBC and the expectations we have for anyone who works with or for us.” The broadcaster added that it had missed opportunities to address his behavior earlier and that it accepted that more “could and should have been done sooner.”

In his deleted post, Mr. Wallace also said that the BBC did nothing to investigate his disability or to provide protections for him because of it. Last year, Mr. Wallace brushed off the claims of inappropriate behavior as coming from “middle-class women of a certain age.”

The Lewis Silkin investigation found little or no training to be in place for handling inappropriate workplace behavior before 2016, and said that concerns taken to the production company were often handled informally.

Shannon Kyle, the ghost writer of Mr. Wallace’s 2012 autobiography, told BBC Newsnight last year that while the two were working on his book, Mr. Wallace had once answered the door wearing only a towel, which he later dropped, and that he touched her thigh and buttocks inappropriately.

The BBC said on Monday that it was not ready to make a final decision on whether it would broadcast the “MasterChef” series that was filmed last year with Mr. Wallace as a presenter.