In a long-ranging and profanity-laced three-hour interview, the younger Biden revealed his father was “tired as s—” during the debate.
“They give him Ambien to be able to sleep,” he told YouTube channel Channel 5.
“He gets up on the stage and looks like he’s a deer in the headlights, and it feeds into every f—ing story that anybody wants to tell.”
The then-president’s dire debate performance led to a litany of prominent Democrats to call for him to retire.
But Biden launched a passionate defence of his father and tore into Democratic heavy-hitters who pushed him to drop out of the race.
“F— him and everyone around him,” Biden said of Clooney.
“What right do you have to step on a man who’s given … his f—ing life to the service of this country and decide that you, George Clooney, are going to take out basically a full page ad in the f—ing New York Times.”
Biden took particular issue at Clooney claiming the then-president did not recognise him at a fundraiser.
He also vociferously tore into senior Democratic consultants James Carville, David Axelrod, David Plouffe and the hosts of popular podcast Pod Save America.
“James Carville, who hasn’t run a race in 40 f—ing years and David Axelrod, who had one success in his political life,” he said.
“And that was because of Barack Obama not because of f—ing David Axelrod.”
“And the Pod Save America guys who were junior f—ing speechwriters on Barack Obama’s Senate staff who have been dining out on the relationship with him for years.”
“They can treat it but it’s not curable,” Biden said.
“But seeing him day-to-day he’s doing well.”
Biden also gave a full-hearted defence of illegal immigrants in America.
“How do you think your hotel gets cleaned? How do you think you got food on your f—ing table? Who do you think washes your dishes?
“Who do you think is here by the f—ing sheer f—ing grit and will that they figured out a way to get here because they thought they could get themselves and their families a better chance?”
The younger Biden became tabloid fodder in the past decade, with much attention drawn to his legal battles and his addiction to crack cocaine and alcohol.
He said he has been sober for more than six years.