Criminal charges have been recommended against “ringleader” Donald Trump after a damning investigation found the former US president “summoned the mob” to Capitol Hill.

The House committee probing the January 2021 insurrection held its last meeting on Tuesday morning (AEDT), after 18 months of interviews and court battles.

In a key milestone in its pursuit of Mr Trump, the panel voted unanimously to approve its historic report which goes into hundreds of pages (and will be publicly released on Wednesday local time).

The panel also called for criminal referrals to be sent to the Justice Department against Mr Trump.

The final meeting of the House select committee investigating the attack on the US Capitol. Photo: Getty

The charges include obstructing an official proceeding, defrauding the US, making false statements and giving aid or comfort to an insurrection, CNN reports.

“Ours is not a system of justice where foot soldiers go to jail and the masterminds and ringleaders get a free pass,” said Democrat Maryland Jamie Raskin, who sits on the committee.

But while potentially damaging to Mr Trump’s bid for the White House in 2024, any referrals would be non-binding.

The Justice Department will decide itself whether to pursue any prosecutions recommended by the committee.

Committee chairman Bennie Thompson said he was “convinced” federal prosecutors would take up the case because the panel had gathered a huge weight of evidence, CNN reports.

“I’m convinced that now that our committee has released our information, they will take the information that we’ve shared with them and proceed with the investigation,” Mr Thompson said.

“No one – including a former president – is above the law.”

The Democratic-led panel has spent 18 months probing the unprecedented attempt to prevent the peaceful transfer of power by thousands of Mr Trump’s backers.

The assault was inspired by the Republican’s false claims that his 2020 election loss to Democratic President Joe Biden was the result of widespread fraud.

Mr Thompson said the panel’s findings showed Mr Trump had “summoned a mob” to the Capitol, knowing they were “armed and angry”.

“I believe nearly two years later, this is still a time of reflection and reckoning,” he added.

“If we are to survive as a nation of laws and democracy, this can never happen again.”

Representative Liz Cheney, one of two Republicans on the committee, said: “Among the most shameful of this committee’s findings was that President Trump sat in the dining room off the Oval Office, watching the violent riot at the Capitol on television.”

The select committee’s work is one of a series of investigations into the riot.

Five people, including a police officer, died during or shortly after the incident and more than 140 police officers were injured. The Capitol suffered millions of dollars in damage.

Donald Trump wants to run for president again in 2024. Photo: Getty

A jury has already found members of the right-wing Oath Keepers militia guilty of sedition for their role in the attack.

A special counsel, Jack Smith, is also leading probes into Mr Trump’s efforts to overturn his loss and his removal of classified documents from the White House.

Mr Trump has faced a series of legal problems since leaving office. His real estate company was convicted on December 6 of carrying out a 15-year-long criminal scheme to defraud tax authorities.

Mr Trump has dismissed the many investigations he faces as politically motivated. He says the January 6 committee, dominated by Democrats, is biased against him.

“The highly partisan Unselect Committee is illegally leaking confidential info to anyone that will listen,” the former president wrote on his Truth Social platform before the meeting.

“How much longer are Republicans, and American Patriots in general, going to allow this to happen.”

-with AAP