WASHINGTON, Dec 13, 2024 (BSS/AFP) - Undercover FBI agents were not present during the 2021 attack on the US Capitol by Donald Trump supporters, a Justice Department watchdog said Thursday in a report debunking a popular right-wing conspiracy theory.

"We found no evidence in the materials we reviewed or the testimony we received showing or suggesting that the FBI had undercover employees in the various protest crowds, or at the Capitol, on January 6," Justice Department inspector general Michael Horowitz said in an 88-page report.

Thousands of Trump supporters stormed the US Capitol on January 6 in a bid to prevent congressional certification of Democrat Joe Biden's election victory.

Right-wing media and even some Republican lawmakers have spuriously claimed that undercover FBI agents provoked the attack on Congress, which followed a fiery speech by Trump in which he falsely claimed the election had been stolen.

The inspector general said that while no undercover FBI agents were present at the Trump rally or the Capitol, 26 FBI informants known as confidential human sources (CHS) were in Washington at the time.

Three of the informants had been tasked with reporting on domestic terrorist suspects while the others were there on their own.

"None of these FBI CHSs were authorized to enter the Capitol or a restricted area, or to otherwise break the law on January 6, nor was any CHS directed by the FBI to encourage others to commit illegal acts on January 6," the report said.

The inspector general also said there had been an intelligence-gathering failure by the FBI ahead of the January 6 attack.

"While the FBI undertook significant efforts to identify domestic terrorism subjects who planned to travel to the Capital region on January 6," the report said, "the FBI did not take a step that could have helped the FBI and its law enforcement partners with their preparations.

"Specifically, the FBI did not canvass its field offices in advance of January 6, 2021, to identify any intelligence, including CHS reporting, about potential threats to the January 6 Electoral Certification," it said.

FBI deputy director Paul Abbate was quoted as saying this was a "basic step that was missed" in "understanding the threat picture prior to January 6."

Trump was impeached by the Democratic-majority House of Representatives following the attack on the Capitol, but acquitted by the Senate.

He is to return to the White House on January 20 after defeating Vice President Kamala Harris in the November presidential election.

More than 1,500 people have been charged in connection with the assault on Congress. Trump has lauded them as "patriots" and "political prisoners" and pledged to pardon many of them when he returns to the White House.