The CNN anchor and Top Gear host have been rivals since Clarkson responded to an unflattering column Morgan had written by punching him in front of reporters at the British Press Awards ... in 2004.
Apparently still incensed by the sight of the 48-year-old news man, Clarkson tweeted a photo of Morgan and called him a "monumental tw*t."
"I cannot wait for the day he goes to prison," the 53-year-old BBC host added.
Clarkson's comment sparked an hours-long verbal sparring match over the pair's respective viewership, Twitter followers and job security.
"You had your chance @JeremyClarkson," Morgan hit back. "Unfortunately you punch like a muscle-depleted chihuahua. So pipe down, you gnarled old fool."
"Americans. Don't trust Piers Morgan. He knows how to hack your phone and will fuck up your army for a buck," Clarkson wrote.
"And why are you issuing advice to Americans @JeremyClarkson ? They've never heard of you," Morgan responded. "I wonder if poor old @JeremyClarkson 's little hissy fit today is connected to Top Gear's disintegrating ratings & rumours it may be axed?"
"I'm going to bed now, happy at the news from CNN insiders that Piers Morgan will soon be sacked," Clarkson said.
Morgan's weekend tiff with Clarkson followed another social media spat with Sarah Palin, who turned down an offer to appear on his show with a biting Facebook message.
Oh dear Piers, thank you so much for all your invitations to appear on your shambolic show, including the adoring message you sent. But is it still any wonder why I've politely responded that I'm too busy doing, um, er... pretty much anything to accept the invite? (At least I didn't tell you to "get stuffed".) And to all our British friends: we ask, what did your friends across the pond ever do to you to deserve your Piers?
The post was accompanied by a photo of her posing with a dead bear and a gun.
"The offer to come on my show still stands. Like I said, we'd have fun....if you've got the guts to do it, Morgan responded. "Being called 'shambolic' by @SarahPalinUSA is most amusing. I wonder if she can see irony from her house?"