Washington DC - President Donald Trump used a black-tie dinner event on Saturday as an opportunity to slam his predecessor Joe Biden as "stupid" and "mean" in a bizarre and expletive-ridden rant.

Trump was speaking at the American Cornerstone Institute's fourth annual Founders Dinner, an event organized by Dr. Ben Carson, who is both the institute's founder and Trump's Housing Secretary.

"You know, Biden was always a mean guy but never a smart guy," the 79-year-old said, going off script as he often does.

"You know, even if you go back 30 years ago, 40 years ago, he was a stupid guy."

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"He was always a mean son of a b****," Trump said, turning up the heat. "How's it working? Not working too well for him now. When you start feeling sorry for him, remember he was a bad guy."

Trump then returned to the topic of his task force to eradicate "anti-Christian bias" in the US, claiming that his administration is "bringing religion back to our country."

Biden's cancer diagnosis has done little to stop Trump from repeatedly attacking him, spreading unhinged conspiracy theories and even hinting at possible prosecution due to his predecessor's use of autopen to sign presidential orders and legislation.

He regularly makes reference to Biden's intelligence, accusing him of being "low-IQ" and even shared wild posts alleging that the former president died and was replaced by a robot clone in 2020.