As the House committee investigating the attack on the US Capitol by extremist supporters of Donald Trump prepares to start public hearings next week, the former president called the insurrection on January 6, 2021, a hoax.

Trump spoke at a rally in Wyoming on Saturday night in support of the Republican primary challenger in the midterm elections to congresswoman Liz Cheney. Cheney sits on the committee and has been vilified by Trump since she voted in favor of his historic second impeachment over the insurrection.

Addressing the sub-capacity crowd at a rally in Casper for Republican candidate Harriet Hageman, Trump slammed Cheney, saying: “As one of the nation’s leading proponents of the insurrection hoax, Liz Cheney has pushed a grotesquely false, fabricated, hysterical partisan narrative.”

He added: “Look at the so-called word insurrection, January 6 – what a lot of crap.”

Trump was impeached by the House of Representatives a week after a violent mob broke into the US Capitol to try in vain to prevent a joint session of congress certifying Democrat Joe Biden’s victory over Republican Trump in the 2020 presidential election.

Trump was accused of inciting the deadly insurrection because he held a rally near the White House that morning, during which he urged the crowd to go to the Capitol and “fight like hell” to overturn the election result.

Then as the violent mob, many carrying Trump banners, broke into the Capitol and rampaged through corridors, offices and chambers, attacking vastly outnumbered police officers and sending Democrats and Republicans fleeing for their lives, Trump ignored calls from colleagues and relatives to publicly call his supporters off and only hours later went on TV mildly telling people to “go home”.

Trump was acquitted at his impeachment trial by the US Senate. A bipartisan Senate report later linked seven deaths to the Capitol attack on January 6.

Lawmakers called for an independent commission to be created, similar to one set up after the terrorist attacks on the US on September 11 2001, to investigate the events on and leading up to January 6 and the involvement of the Trump White House.

Republicans in the Senate killed that move so the House last summer formed a select committee to investigate the insurrection, chaired by Mississippi Democratic congressman Bennie Thompson but also including Republicans Adam Kinzinger and Cheney, the daughter of former vice-president Dick Cheney.

The committee has since gathered mountains of evidence and taken testimony from numerous witnesses behind closed doors, while being stonewalled by many senior Republicans, and accuses Trump of attempting to lead a type of coup.

The committee is due to hold a series of public hearings beginning 9 June and expects to present a report before the midterm elections in November. Separately, the Department of Justice is also investigating events on and surrounding the Capitol attack, led by the US attorney general, Merrick Garland.

At the rally in Wyoming , Trump appeared to lament the treatment of those arrested for taking part in the Capitol attack, while falsely claiming that anti-fascist and Black Lives Matter movement anti-racism activists “have killed plenty”.

“Look what they are doing to these people,” he said.

More than 800 people have been charged with federal crimes relating to the riot on January 6, in the biggest federal criminal investigation since the 9/11 terrorist attacks.

At least 300 have already pleaded guilty, mostly to misdemeanors, and nearly 20o have been sentenced. Approximately 100 others have trial dates.

In the latest court cases, Matthew Mark Wood, of North Carolina, pleaded guilty last Friday to charges that he stormed the Capitol, including a felony charge of obstructing an official proceeding, and will be sentenced in September.

He entered the Capitol by climbing through a smashed window and followed others who had overcome police through corridors and into House speaker Nancy Pelosi’s offices.

Also last Friday Matthew Joseph Buckler, of Maryland, pleaded guilty and will be sentenced in July for “parading, demonstrating or picketing in a Capitol building” after also entering through a window breached by the mob.

It was ruled in court that the former top leader of the far right, violent group the Proud Boys, Henry “Enrique” Tarrio, will remain jailed while awaiting trial on charges that he conspired with other members of the extremist group to take part in the insurrection.

Tarrio, a south Florida resident, has been indicted on charges including conspiracy.