The Apprentice star made an appearance on the news channel, which launched on Sunday (13 June) with a special show hosted by its chairman, the broadcaster Andrew Neil.
Sugar was interviewed by Dan Wootton, and during the segment, he hit out at Markle for the televised conversation she had with Oprah Winfrey in March.
Markle told Winfrey that she was denied mental health care for suicidal thoughts she had while living at Buckingham Palace. Sugar combatted this in the GB News interview by saying that he believes Markle would have had access to the best mental heath care if she wanted it.
Sugar, who supported Piers Morgan in his controversial criticism of Markle, said he stands by the fact that he thinks Markle was “lying” about this.
He said: “Buckingham Palace and all these places where they live... doctors are visiting privately every single day of the week, so if she had something wrong with her, I’m absolutely sure that a psychiatrist or psychotherapist or whatever could have come and visited, and no one would need to know.”
He continued: ”I should imagine that the Queen has had many visits and indeed some other members of the family, have had many visits from doctors. They’re very private and confidential and very carefully conducted. For that reason, and that reason alone, I don’t believe her.”
Those who watched the interview criticised Sugar for his comments, with many highlighting it as an example of why they won’t be tuning in to the news channel again.
“They lost me when they had Alan Sugar on to discuss the validity of Meghan Markle’s mental health issues. Really..?” one angry viewer wrote, with another calling the channel “truly awful”.
“Car crash interview with Alan Sugar,” they added. “Desperately trying to shoehorn a negative comment in about Meghan, every sentence mentions woke, liberal, left and elite. What an utter shower of s***.”
One other viewer tweeted: “Turn on GB News just for a gander to be greeted by Alan Sugar saying that Meghan Markle was lying about having mental health issues to a washed up former Sun columnist. I turned off.”
In the same interview, Sugar awkwardly called out Wootton for asking him a “stupid bloody question”.