Gareth Morgan has lashed out at his former political party, calling them "losers" and "degenerate".
In response, the Opportunities Party (TOP) has retweeted comments calling Dr Morgan "socially retarded" and implied he's an old man shouting at people to get off his lawn.
Dr Morgan set up TOP in 2016, spending millions of his own fortune in a failed attempt to get into Parliament at the 2017 election. He stepped down as leader a few months later, and severed all ties in March this year.
But the divorce isn't going well. Dr Morgan ripped into his former colleagues last week, telling RNZ they were a "group of grovelling, compromising political aspirants" who lack talent and don't deserve to even contest the 2020 election, let alone make it into Parliament.
TOP shared the RNZ story on its Twitter account, commenting: "You mad dad?"
Dr Morgan, who's reportedly currently on a motorcycle tour across Asia, took a few days to respond - but when he did, he didn't hold back.
"TOP doesn't deserve to degenerate into a Kumbaya commune standing in a circle holding hands and repeating the policies of TOP2017 via Gregorian chants," he wrote.
"FFS where's the vitality, the guts to be different & lead the policy conversation? What losers."
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Dr Morgan even found time on Monday morning to respond to one of his critics on Twitter after TOP retweeted them.
"Gareth Morgan's description of the current @top_nz party as 'obsequious', 'reprobates' etc is mostly evidence of how Morgan himself was unfit to be in politics," wrote Bob Miller, a man who appears to be based in New York and has only 22 followers. "He's obv socially retarded but wants to shock ppl like Sir Bob Jones. Unlike Jones, he's got no grasp of humour."
"What a load of shit," Dr Morgan responded. "Transformational politics is worth pursuing, just wanting to be a politician perpetuates the mediocrity establishment parties have perfected.
"Read the f**king policies you dropkick, use your brain and tell us which isn't worth pursuing - you're not fit to vote."
TOP hit back, asking Dr Morgan how his retirement was going alongside an animated gif of an elderly cartoon man yelling "get off my lawn!" - perhaps a reference to Dr Morgan's recent purchase of a golf course, from which has banned politicians and cats.