Jacob Anthony Chansley, aka "QAnon Shaman" (center), during the US Capitol riot on January 06, 2021. Photo: AFP

Donald Trump deluged aides with wild voter fraud conspiracy theories after losing the 2020 US election, his top law-enforcement official said in testimony revealed Monday by a congressional probe which the ex-president branded a "mockery of justice."

Appearing in a pre-recorded deposition at a congressional hearing into the 2021 assault on the US Capitol, former attorney general Bill Barr described his then-boss as having no interest in the facts that debunked his groundless narrative.

"I was demoralized because I thought, boy... he's become detached from reality if he really believes this stuff," Barr told the House committee investigating the January 6 insurrection by supporters of Trump.

"When I went into this and would tell him how crazy some of these allegations were, there was never an indication of interest in the actual facts," said Barr, who likened addressing Trump's avalanche of false allegations with playing the game "whack-a-mole."

The panel is holding six hearings throughout June to outline its case that the riot at the seat of US democracy in Washington was the culmination of a seven-step conspiracy by Trump and his inner circle to overturn his defeat to Joe Biden.

Trump ignored repeated warnings from top aides against falsely claiming the November 2020 election was stolen, according to testimony unveiled by the panel.

"We will tell the story of how Donald Trump lost the election - and knew he lost the election - and as a result of his loss, decided to wage an attack on our democracy," the committee's Democratic chairman Bennie Thompson said in his opening remarks.

Trump released his first extended reaction to the probe Monday evening, with a rambling 12-page statement in which he called the panel a "mockery of justice" and a "Kangaroo Court hoping to distract the American people from the great pain they are experiencing."

The second of six planned hearings was shown videotaped accounts from the former president's advisors, including Barr and campaign manager Bill Stepien, saying they repeatedly counseled him not to declare victory on election night because he hadn't won - but that Trump went ahead anyway.

Thompson's deputy on the panel, Republican lawmaker Liz Cheney, said Trump chose to listen to the advice of "apparently inebriated" former New York mayor Rudy Giuliani "to just claim he won, and insist that the vote counting stop - to falsely claim everything was fraudulent."

Trump started pushing what came to be known as his "Big Lie" around 2:30 am on November 4, 2020, prematurely declaring victory on the night of an election he ultimately lost to Biden by 7 million votes.

AFP