Donald Trump should never be allowed to run for public office again after inciting an insurrection, lawmakers investigating last year'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.

Multiple investigations

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 -- obstruction of an official proceeding, conspiracy to defraud the United States, making false statements to the government and inciting insurrection.

Essentially, Trump is accused of spending months lying to supporters that the 2020 election was stolen from him, trying to corrupt federal and state officials, whipping up a mob to storm the Capitol despite knowing it was armed and of doing nothing for hours to stop the violence.

The panel has begun turning over transcripts and other documents to independent prosecutor Jack Smith, who is overseeing federal probes into Trump's role in the riot and his handling of government secrets improperly stored at his Florida beach club.

"If the evidence is as we presented it, I'm convinced the Justice Department will charge former President Trump," committee chairman Thompson told CNN ahead of the report's release.

The twice-impeached 76-year-old Trump is also facing criminal and civil investigations into his business practices and efforts to overturn his election defeat in the swing state of Georgia.