Meghan Markle reportedly submitted a complaint to ITV about Piers Morgan's behaviour on Monday's Good Morning Britain.
The formal complaint is said to have sparked a chain of events that led to Morgan quitting the show yesterday after more than five years in the role.
On Monday's GMB, the 55-year-old delivered a withering assessment of Markle and Prince Harry's tell-all interview with Oprah Winfrey, questioning their credibility and describing them as "completely self-serving".
One comment in particular attracted a lot of heat when, straight after showing a clip in which Markle admitted feeling suicidal, he said: "OK, again, let's have the names. Who did you go to? What did they say to you? I'm sorry, I don't believe a word of what she says, Meghan Markle. I wouldn't believe it if she read me a weather report."
On Tuesday's show Morgan clarified that his remarks were referring to the interview in general rather than her thoughts of suicide, but tempers remained high and in the same programme he stormed off set after being taken to task by colleague Alex Beresford.
According to The Telegraph, ITV is thought to have received a complaint from the Duchess of Sussex about Morgan's behaviour and as a result asked him to make an on-air apology.
Morgan then refused and instead handed in his resignation to the broadcaster, who immediately terminated his contract with the breakfast show.