Scott Perry, a Pennsylvania Republican and the first sitting member of Congress to be requested to provide documents and sit for an interview with the committee investigating the Capitol riot, said on Tuesday he would not comply with the panel.

The news came shortly after Donald Trump provocatively announced that he will hold a press conference at his Mar-a-Lago resort on 6 January, the first anniversary of the deadly attack on Congress.

Perry’s refusal to appear sets up a potentially fraught battle if the panel decides to subpoena him and he – like other Trump allies – decides to ignore that too.

The committee has already recommended other no-shows, such as Trump aide Steve Bannon, be prosecuted for their non-compliance.

Perry claimed the 6 January committee was “illegitimate, and not duly constituted under the rules of the US House of Representatives”.

Successive court rulings have said that the committee was properly formed and does have the investigative powers it is using.

The House speaker, Nancy Pelosi, rejected an attempt by the minority leader, Kevin McCarthy, to put Republicans including Jim Jordan of Ohio – a close Trump ally and a subject of investigation regarding the Capitol attack – on to the 6 January committee. Only two Republicans, Trump critics Liz Cheney and Adam Kinzinger, are now part of its work.

Trump announced his press conference in a statement replete with familiar invective and lies about supposed electoral fraud and the House committee.

“I will be having a news conference on 6 January [2022] at Mar-a-Lago to discuss all of these points, and more,” he said.

“Until then, remember, the insurrection took place on 3 November, it was the completely unarmed protest of the rigged election that took place on 6 January.”

Five people, including a Trump supporter shot by law enforcement and a Capitol police officer, died around the events of 6 January 2021, when a pro-Trump mob stormed Congress after he told supporters to “fight like hell” to overturn his defeat by Joe Biden.

More than 700 people have been charged with offenses connected to the riot. Most rioters were not armed with guns but attacked police with other weapons. Guns and explosives were found and bombs planted. On Monday, one rioter who attacked police was sentenced to more than five years in jail.

Trump was impeached for inciting an insurrection but acquitted at his Senate trial when enough Republicans stayed loyal.

His continued presence in national politics and apparent intention to run for president again has stoked jagged divides which some observers fear point the US towards serious discord or even civil war.

On Monday night the disgraced former Fox News host Bill O’Reilly, with whom the former president has staged an arena tour, said Trump was “gonna run again”.

“I’m trying to tell President Trump, run on your record,” O’Reilly told NewsNation. “He’s gonna run again. I said, Run on your record, because your record’s pretty darn good.’”

Trump seems determined to run, or merely to retain control of the Republican party, through stoking division and anger with false claims about the election and the most serious attack on the US Capitol since the war of 1812.

In stark contrast, Pelosi has announced that Congress will mark the first anniversary of 6 January in a spirit of “solemn observance”.

“Preparations are under way for a full program of events,” she said, “including a discussion among historians about the narrative of that day; an opportunity for members to share their experiences and reflections from that day; and a prayerful vigil in the evening.”

The 6 January committee also expects to stage events in the new year, with public hearings as it closes in on Trump’s role in the riot. On Sunday, Kinzinger said the panel would determine if Trump committed a crime.

“Nobody is above the law,” he said. “He’s not a king. Former presidents, they aren’t former kings.”

Trump has sued, so far unsuccessfully, to stop the committee accessing White House documents from his time in power. Two of his closest aides are in serious legal jeopardy for taking similar stands.

Bannon has pleaded not guilty to contempt of Congress for refusing to cooperate with the 6 January committee. He faces a fine and jail time if convicted.

The House has recommended the same criminal charge for Mark Meadows, Trump’s last chief of staff and a former congressman.

On Monday, citing sources close to Trump, the Guardian revealed his deepening fear as the 6 January committee continues its work.

“The former president’s anger largely mirrors the kind of expletives he once directed at the Russia inquiry and the special counsel investigation [led by Robert Mueller] when he occupied the White House,” the Guardian reported.

“But the rapidly accelerating investigation into whether Trump and top aides unlawfully conspired to stop the certification of Joe Biden’s victory at the 6 January joint session appears to be unnerving him deeply.”

On Twitter, Peter Strzok, a former FBI agent and member of the special counsel’s team, wrote: “Almost as if – what did he say about Mueller? – ‘I’m fucked.’”