Lawmakers investigating last year's assault on the US Capitol recommended Monday that Donald Trump be charged with multiple offenses including insurrection -- raising the stakes in a parallel criminal investigation that could put the former president in jail.

The House of Representatives select committee called for the indictment -- as well as charges of obstruction of an official proceeding and conspiracy to defraud the United States -- after an 18-month probe into the storming of Congress on January 6, 2021.

At least five people died after a mob whipped up by Trump's false claims of a stolen election, and directed to march on Congress by the defeated president, ransacked the seat of US democracy in a thwarted bid to prevent the transfer of power to President Joe Biden.

The bipartisan committee voted unanimously to refer the charges to the Justice Department after opening remarks by vice-chair Liz Cheney in which she accused Trump of "a clear dereliction of duty" in failing to immediately attempt to stop the riot and called him "unfit for any office."

"No man who would behave that way at that moment in time can ever serve in any position of authority in our nation again," she said.

The referrals are seen as largely symbolic, as the panel has no control over charging decisions, which rest with the Justice Department.

Jack Smith, a largely independent special prosecutor appointed by Attorney General Merrick Garland, is leading his own investigation into Trump related to the 2020 election.

- Major blow -
Trump issued a statement claiming that the purpose of the investigation was to "keep me from running for president because they know I'll win" and that any prosecution would be "a partisan attempt to sideline me."

Trump's approval ratings are underwater -- at minus-20 percentage points in the RealClearPolitics average, compared with minus-eight percent for Biden.

But the lawmakers' move is nevertheless historic, as Congress has never made a criminal referral against a sitting or former president, and it will add to the clamor among Trump's opponents for prosecution.

It is also a major blow to Trump amid a series of missteps in the weeks since he announced a comeback bid for the White House -- including the Republicans' poor midterm election showing in states where the tycoon endorsed candidates.

Charges could result in a ban from public office for the 76-year-old Republican, who still wields considerable power in the Republican Party, and even prison time.

"To cast a vote in the United States is an act of faith and hope," committee chairman Bennie Thompson said.

"That faith in our system is the foundation of American democracy. If the faith is broken, so is our democracy. Donald Trump broke that faith."

The seven Democratic and two Republican panel members are winding down their work before the end of the year, and have compiled their findings into an eight-chapter report set to be released on Wednesday.

The committee's case is that Trump "oversaw and coordinated a sophisticated seven-part plan to overturn the presidential election and prevent the transfer of presidential power."

- 'Trump knew he lost' -
Investigators say the plot began with Trump's campaign to spread allegations he knew were false that the election was marred by widespread fraud.

He is accused of trying to corrupt the Justice Department and of pressuring his vice president Mike Pence, as well as state election officials and legislators, to overturn the vote by violating the Constitution and the law.

Trump is also accused of summoning and assembling the mob in Washington, and directing it toward the Capitol despite knowing it was armed with assault rifles, handguns and numerous other weapons.

And for hours he ignored pleas from his team to take action to stop the violence, lawmakers say.

Democratic panel member Zoe Lofgren said Trump's false fraud claims -- far from being spontaneous -- were part of a deliberate attempt to sow distrust in democracy that began long before the insurrection.

Lofgren repeated the panel's suggestion that Trump allies had engaged in witness tampering, alleging that someone linked to the former president had offered potential employment to a witness prior to their testimony.

Lofgren said a witness was also told by a lawyer linked to Trump that she could pretend to not remember facts as she was giving evidence.

Lofgren also returned to an accusation previously leveled by the panel that Trump had "raised hundreds of millions of dollars with false representations made to his online donors."