Replays revealed the YouTube sensation landed an accidental but illegal elbow, which consequently caused the KO.
KSI broke his silence on social media to claim Fournier “fell into” his forearm and voiced his “disappointed” in the ending of the bout.
But Paul, 26, hit back: “Why you lying still? No part of your glove made contact with Joe’s face on that elbow.
“That was not a hook. That was straight up a right elbow to the jawbone. Good form but wrong sport. Your whole promotion is sham.
“Bad look for the sport of boxing. Your “commission” PBA should hold itself to a higher standard.
“I hope England Boxing starts to oversee this product and makes it safer for everyone.”
Fournier, 40, accused KSI, 29, of cheating and demanded a disqualification or rematch be called.
And the Professional Boxing Association – who sanctioned the fight – confirmed an appeal has been lodged and will conclude by Friday.
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KSI came into the bout with five wins in the ring and one draw compared to nightclub businessman-turned 9-0 boxer Fournier.
And he was left underwhelmed in the contentious ending of what was the biggest night in his boxing career.
KSI posted on Twitter: “I worked very hard for this fight and had an intense and gruelling camp.
“There’s no better feeling than being in that ring and having my hand raised in front of my loyal and amazing fans who I appreciate so much.
“Unfortunately the victory which was inevitable no matter what, is tarnished and I hate that. It sucks!
“After landing my overhand he was pretty much out on his feet and I went for a short right hook as Joe clinched me and fell into me.
“I landed that hook and my glove made contact but appears to have been followed by unintentional contact with my forearm.
“I’m gutted that it’s not as clean a win as I wanted and it feels like it diminishes my hard work with my trainers.
“Either way I hope you enjoyed the show and appreciate the support. Sorry to all the fans disappointed with it. No one is more so than me.”
