During the show, Jack was chatting to the band when he referenced their infamous feud with Piers over a naked photoshoot they’d done.
“Piers Morgan. He didn’t like that picture where you stripped off naked,” Jack said. “Which is weird because four chins and voluptuous breasts – it must have been like looking in the mirror.”
Piers did not take the joke lying down, reigniting the row with Little Mix on Twitter.
He tweeted: “Shocked and disappointed to see Little Mix laugh as Jack Whitehall fat-shames me on national television.
“It’s just this kind of public negative body image mockery that the same Little Mix campaigned against and of which I am now a victim. Shame on you, ladies!”
He added: “And as for chins, at least I’ve got some, you chinless little weed Jack Whitehall.”
As of yet, Little Mix and Jack are yet to respond to Piers.
The original Little Mix image was used to promote the song Strip from their album LM5, while an accompanying video sees them surrounded by women of different ages, ethnicities and body types, including their mothers.
Of the music video, Jesy told HuffPost UK: “It’s so real, like, you can’t get any realer than this video.
“Nothing’s been airbrushed, what you see is what you get, and it’s just about women owning it and feeling confident and loving every single part of their body.”