The Duchess of Sussex contacted ITV personally on Monday to warn that Piers Morgan’s dismissive attitude towards her Oprah Winfrey interview could prove damaging to others suffering with mental health problems.

The Duchess (39) is understood to have been briefed on Morgan’s comments on Good Morning Britain when she woke up after the two-hour interview aired in the US.

The outspoken presenter told viewers he “didn’t believe a word” of what she told the US chat show host, including her claim that she was not supported by Buckingham Palace when experiencing suicidal thoughts.

The Duchess’s decision to lodge a formal complaint was not related to his personal criticism of her, reporters understand.

But she was concerned that his comments could have a detrimental effect on others who were experiencing mental health problems. She also feared that his broadside might influence the opinions of others on mental health.

On receiving her email, ITV bosses asked Morgan to apologise to the Duchess during Tuesday’s show – but he refused. The former Daily Mirror editor then quit, after storming off the set following a row with weather presenter Alex Beresford.

He said on Tuesday’s episode that he still had “serious concerns about the veracity of a lot of what” the Duchess had said, but that it was “not for me to question if she felt suicidal”.

ITV, which bought the rights to the Winfrey interview for a rumoured stg£1m, later confirmed he had quit, ending his six-year tenure on the show.

The development followed Buckingham Palace’s reaction to the Sussexes’ interview, which said the royal family was ”saddened to learn the full extent of how challenging the last few years have been for Harry and Meghan”. The pregnant Meghan claimed during the interview that she was nearly driven to suicide by life in the British royal family. She said she desperately sought help from palace aides, but that her pleas fell on deaf ears.

Morgan said on Monday’s show: “I’m sorry, I don’t believe a word she says. I wouldn’t believe her if she read me a weather report.”

In a tweet later that morning, he referred to her as the “Pinocchio Princess”.

Speaking outside his London home yesterday, Morgan repeated his comments, saying: “If I have to fall on my sword for expressing an honestly held opinion about Meghan Markle and that diatribe of bilge that she came out with in that interview, so be it.”

He reiterated it again on Twitter, saying: “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.”

Morgan quoted Winston Churchill, who said: “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.”

He later revealed that Good Morning Britain had for the first time beaten BBC Breakfast in the ratings on Tuesday, adding: “My work is done.”

Mind, a leading mental health charity, was among those who criticised Morgan. It said: “It’s vital that, when people reach out for support or share their experiences of ill mental health, they are treated with dignity, respect and empathy.”

Dame Carolyn McCall, ITV chief executive, said she “completely believed what [the duchess] says”, adding that ITV was “totally committed to” mental health.

Morgan faces an Ofcom investigation after the regulator received 41,000 complaints over his comments.

He has not hidden his disdain for the Duchess after accusing her of “ghosting” him when she met Prince Harry.