The duo have been arguing on Twitter over the Good Morning Britain presenter’s appearance on a US chat show when he was sworn at by a fellow guest.
It led to a back and forth on the social media site, but the journalist took it to the next level by hitting out at Rowling and her fellow liberals in a US interview.
Appearing on Fox News, Morgan was asked by host Tucker Carlson why the novelist and screenwriter appeared “so mad”.
Carlson asked: “She’s really upset. More upset than I’ve ever seen a class of people ever be upset.
Piers Morgan has urged JK Rowling to 'shut up'
You are the worst celebrity political pundit on the entire planet
“What is that about? Why are people you’d think would be in a pretty good mood because they’re insulated from every economic variation you can imagine, why are they so mad right now?"
Morgan cited her voting record and attitude before labelling her “the worst celebrity political pundit on the entire planet.”
He said: ‘Well, she’s a serial loser. The more that JK Rowling has screamed at people to vote in a certain way, the more her people have lost.
“So, let’s go through the checklist of glorious failure. She backed Ed Miliband in the last UK election, he got thumped by David Cameron, she then moved on to back the Remain campaign to stay in Europe and obviously we Brexit-ed so she lost that as well.
Piers Morgan is friends with US President Donald Trump
“She then threw her substantial political influence behind Hillary Clinton, shouting down anybody that disagreed with her and of course Hillary got a drubbing as well from a guy who was a non-politician.
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“So if you’re JK Rowling you’re three for three, you are the worst celebrity political pundit on the entire planet.
“I understand her pain, but she is synonymous with this absurdly arrogant, supercilious kind of view of so many celebrities now on the left and, as you know, I’m more liberal than I am right but I cannot stand this anti-Trump hysteria which is now infesting every part of the political debate.”
But the 51-year-old was not finished there. He added he had never ready Harry Potter and urged her to “shut up”.
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He said: “Just go and write about Hogwarts, wizards, whatever they are, I’ve never read a word of Harry Potter. Just go and immerse yourself in the world of muggles, or whatever they are, and shut up.”
Piers Morgan came to blows with Australian comedian Jim Jefferies as the pair appeared on HBO's Real Time With Bill Maher last week.
Morgan, who regularly defends his friend Donald Trump, got into a heated debate with Jefferies, 39, when he insisted that the President's immigration order was "not a Muslim ban".
Jefferies then snapped: “Oh, f**k off. This is what you do, Piers. You say ‘He hasn’t done this, he hasn’t done that, he’s not going to do all these things’.
Rowling poked fun at the clash on Twitter, which stirred the torrent of abuse from Morgan.
GMB: Piers Morgan & Susanna Reid take on politicians Tue, January 24, 2017
Good Morning Britain hosts Piers Morgan and Susanna Reid talk politics with Theresa May, Nigel Farage, Donald Trump and more.
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Good Morning Britain talks politics with Theresa May, Donald Trump, Nigel Farage, & more
Rowling started off by saying, alongside a clip of last night's row: "Yes, watching Piers Morgan being told to f**k off on live TV is *exactly* as satisfying as I'd always imagined."
Morgan then replied: "This is why I've never read a single word of Harry Potter," before she raged: "Because you had a premonition that one day the author would roar with laughter at seeing you called out for your bulls**t on live TV?”
As a result of the spat, a bookshop owner has been tweeting every line of the first Harry Potter book to Morgan.
Simon Key said he was inspired by the presenter’s comments that he would never read Rowling’s books.
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