Former US president Donald Trump on Friday denounced the congressional investigation into the attack on the US Capitol by his supporters as a "show trial" and a "witch hunt".
Trump, in a letter to Bennie Thompson, the chairman of the January 6 committee, did not address the subpoena for him to testify that was issued by the House panel on Thursday.
Instead, the former Republican president repeated his criticisms of the committee and his false claims that the 2020 election won by Democrat Joe Biden was "rigged and stolen".
"You have not spent even a short moment on examining the massive Election Fraud that took place during the 2020 Presidential Election," Trump wrote.
"The Unselect Committee has perpetuated a Show Trial the likes of which this Country has never seen before," he said. "There is no Due Process, no Cross-Examination, no 'real' Republican members, and no legitimacy since you do not talk about Election Fraud.
"It is a Witch Hunt of the highest level, a continuation of what has been going on for years," Trump said.
He also defended the rioters who attacked Congress on January 6, 2021 as it was certifying Biden's election victory, calling them "patriots" and "concerned American citizens".
"You have not gone after the people that created the Fraud, but rather great American Patriots who questioned it, as is their Constitutional right," Trump said.
"These people have had their lives ruined as your Committee sits back and basks in the glow."
The January 6 panel, holding what is expected to be its final hearing before the November midterm elections on Thursday, voted to subpoena Trump to testify.
Trump responded with a post on his Truth Social platform but did not say whether he would agree to appear.
"Why didn't the Unselect Committee ask me to testify months ago?" he said. "Why did they wait until the very end, the final moments of their last meeting?"
The New York Times reported that Trump has been telling aides that he favours testifying if he can do so live, but it is unclear whether the committee would grant such a demand.
Subpoenas from the panel have proved difficult to enforce, with former White House aide Steve Bannon the only person convicted of contempt of Congress so far for refusing to comply.
Across eight hearings in the summer the January 6 panel has unveiled reams of evidence showing the former president's involvement in a labyrinthine series of connected schemes to overturn the election.
Trump, who urged his supporters in a fiery speech near the White House on January 6 to "fight like hell," was impeached for inciting the mob to storm Congress to halt the peaceful transfer of power to Biden.