ITV announced the decision on Tuesday (9 March) evening as Ofcom said it was investigating 41,000 complaints about Morgan’s remarks regarding the Duke and Duchess of Sussex’s interview with Oprah Winfrey.
Morgan co-hosted the popular morning show for six years, alongside Susanna Reid.
So, what did the presenter say about Meghan, why did he leave GMB - and what has the show said in response?
Here is everything you need to know.
What did Piers Morgan say?
A day before he left GMB, Morgan gave a scathing review of Meghan and Harry’s chat with Oprah.
Talking on the morning show after the bombshell interview aired, the controversial host said: “I’m angry to the point of bawling over today. I’m sickened by what I just had to watch.
“This is a two-hour trashathon of our royal family, of the monarchy and everything our queen has worked so hard for and it’s all been done while Prince Philip lies in hospital.
“They trash everybody. They basically make out our Royal family are a bunch of white supremacists by this race bombshell.
“They didn’t name any which one it was, they just throw it out there so it could be anybody.”
Yet viewers were left shocked when Morgan went on to say he didn’t believe Meghan when she revealed she had suicidal thoughts due to struggling with life in the royal family.
Morgan continued: “Who did you go to? What did they say to you?
“I’m sorry, I don’t believe a word she said, Meghan Markle.
“I wouldn’t believe it if she read me a weather report.
“The fact that she’s fired up this onslaught against our Royal family I think is contemptible.”
Social media users were quick to criticise the host’s comments, while ITV CEO Carolyn McCall responded saying the broadcaster would hold talks with Morgan about his remarks about Meghan’s mental health.
Why did Morgan storm off the GMB set?
The controversy continued on Tuesday (9 March), when Morgan engaged in another heated debate about the Duchess of Sussex with GMB colleague Alex Beresford.
The heated exchange led to Morgan dramatically storming off set.
Discussing Harry and Meghan’s interview, Beresford said: “They’ve had an overwhelming amount of negative press.
“There was bad press around the engagement before the engagement, and everything that has followed since has been incredibly damaging, quite clearly, to Meghan’s mental health and also to Harry.”
But things became tense when Beresford addressed Morgan’s disparaging opinion of Meghan.
He continued: “I understand that you don’t like Meghan Markle, you’ve made it so clear a number of times on this programme.
“And I understand you’ve got a personal relationship with Meghan Markle,” he added, “or had one and she cut you off.
"She’s entitled to cut you off if she wants to. Has she said anything about you since she cut you off? I don’t think she has but yet you continue to trash her.”
At this point Morgan stood up and said: “OK, I’m done with this”, and walked off set.
Why did Piers Morgan leave Good Morning Britain?
The journalist’s comments about Meghan’s suicidal thoughts drew criticism from mental health charity Mind, which said it was “disappointed and concerned” by the remarks.
Meanwhile, after Ofcom received thousands of complaints about the comments, a spokesperson for the watchdog said: “We have launched an investigation into Monday’s episode of Good Morning Britain under our harm and offence rules.”
During Tuesday’s (9 March) GMB programme, Morgan directly addressed what he said about the duchess’s mental health.
“When we talked about this yesterday, I said as an all-encompassing thing I don’t believe what Meghan Markle is saying generally in this interview, and I still have serious concerns about the veracity of a lot of what she said,” he told viewers.
“But let me just state on the record my position about mental illness and on suicide.
“These are clearly extremely serious things that should be taken extremely seriously, and if someone is feeling that way they should get the treatment and help they need every time."
But that evening it was announced that Morgan had left his role as co-presenter on the morning show.
An ITV spokesperson said: "Following discussions with ITV, Piers Morgan has decided now is the time to leave Good Morning Britain.
“ITV has accepted this decision and has nothing further to add."
The broadcaster’s CEO has made it clear that ITV takes mental health very seriously.
What has Morgan said since?
As GMB aired on Wednesday (10 March) morning, Morgan posted a fresh statement about his comments regarding Meghan.
Taking to Twitter, he wrote: "On Monday, I said I didn’t believe Meghan Markle in her Oprah interview. I’ve had time to reflect on this opinion, and I still don’t. If you did, OK.
"Freedom of speech is a hill I’m happy to die on. Thanks for all the love, and hate. I’m off to spend more time with my opinions."
The Tweet was accompanied by a picture of Winston Churchill and one of his quotes, which read: "Some people's idea of free speech is that they are free to say what they like, but if anyone says anything back, that is an outrage."
How has Susanna Reid responded?
Speaking on GMB’s first show without Morgan, co-host Susanna Reid addressed his sudden departure from the programme.
The presenter said it would be “very different” without Morgan but “shows go on”
“He is without doubt an outspoken, challenging, opinionated, disruptive broadcaster,” Reid said.
“He has many critics and he has many fans. You will know that I disagreed with him about Meghan’s interview. He himself clarified his comments about her mental health on the show yesterday.
“There are many voices on GMB and everyone has their say. But now Piers has decided to leave the programme. Some of you may cheer and others may boo.
“He has been my presenting partner, Monday to Wednesday, for more than five years and during Brexit and the pandemic and other issues, he has been a voice for many of you and a voice that many of you have railed against.
“It is certainly going to be very different but shows go on and so on we go.”