Former US president Donald Trump speaks at the Mar-a-Lago Club in Palm Beach, Florida, on November 15, 2022. Donald Trump pulled the trigger on a third White House run on November 15, setting the stage for a bruising Republican nomination battle. Photo: VCG

Donald Trump should never be allowed to run for public office again after inciting an insurrection, lawmakers investigating 2021's assault on the US Capitol concluded in their watershed final report.

The recommendation led a list of proposals from the 845-page document aimed at ensuring there is no repeat of the deadly riot the ex-president is accused of orchestrating in a failed bid to cling to power after losing the 2020 election.

"Our country has come too far to allow a defeated president to turn himself into a successful tyrant by upending our democratic institutions [and] fomenting violence," the panel's chairman Bennie Thompson said in an introduction to the report, released late Thursday.

The document urges lawmakers to legislate so that Trump and others who "engaged in insurrection" can be barred from holding office - "whether federal or state, civilian or military."

Trump has announced he intends to run for the White House again in 2024.

The report was the culmination of 18 months of work by congressional investigators who interviewed more than 1,000 witnesses to establish the primary cause of the attack, which they blamed squarely on the Republican billionaire.

The committee also recommended reforms of election law, a federal crackdown on extremist groups and the designation of Congress's certification of presidential elections as a "national special security event" on a par with the annual State of the Union address.

It was the panel's final act before it is disbanded as the House of Representatives switches to Republican control in January. 

The party has opposed the investigation at every step and the switch in the balance of power raises doubts over the possibility of most of the recommendations ever being taken up. 

Trump posted a statement on his Truth Social platform misrepresenting the role of Democratic leadership in security preparations ahead of the attack, and decrying a "witch hunt," as he does with most investigations accusing him of misconduct. 

The report was long on detail but short on new revelations as the committee's seven Democrats and two rebel Republicans had already set out their case against Trump over eight blockbuster public hearings in the summer.

In their final public meeting Monday, the panel referred the tycoon to the Department of Justice on four potential charges, making false statements to the government.