The Ohio Republican Jim Jordan is the second sitting congressman to refuse a request for cooperation from the House select committee investigating the Capitol attack.

In a Sunday night letter to the committee chair, Bennie Thompson of Mississippi, the Trump ally accused the panel of “an outrageous abuse” of its authority.

He also claimed “an unprecedented and inappropriate demand to examine the basis for a colleague’s decision on a particular matter pending before the House of Representatives”.

“This request is far outside the bounds of any legitimate inquiry,” he said, “violates core constitutional principles and would serve to further erode legislative norms.”

Scott Perry of Pennsylvania, who was also closely involved in Donald Trump’s attempt to overturn his election defeat, has also refused to cooperate.

The former Trump strategist Steve Bannon has pleaded not guilty to a charge of criminal contempt of Congress, for refusing cooperation. His trial is set for July.

Mark Meadows, Trump’s final White House chief of staff and a former congressman, has also refused. The committee has recommended a criminal charge.

Citing committee sources, the Guardian has reported that the panel is considering whether Trump himself might be charged with criminal conspiracy.

But Thompson has suggested the panel may have few options to compel testimony from sitting members of Congress. An alternative path may be a series of primetime public hearings, seeking as wide an audience as possible.

In columns for the Guardian, the former Clinton aide Sidney Blumenthal has laid out Jordan’s extensive contacts with Trump before and on 6 January, throughout legalistic efforts to throw out results and the Capitol riot itself.

Blumenthal has also suggested precedent exists for compelling Jordan to testify – in the investigation of John Brown’s anti-slavery raid on Harper’s Ferry, Virginia in 1859.

That event preceded the civil war, fought from 1861 to 1865. Many academics and observers have warned that Trump’s assault on democracy could stoke such conflict.

Five people died and more than 140 police officers were injured around the attack on Congress, which failed to stop the certification of electoral college results. Trump was impeached, for inciting an insurrection, and acquitted.

Jordan, a former wrestling coach and member of the hard-right Freedom Caucus, is a leading Trump ally in Congress.

Kevin McCarthy, the House Republican leader, proposed Jordan as a member of the 6 January committee. Democrats blocked it. Only two Republicans sit on the panel: Trump critics Liz Cheney, of Wyoming, and Adam Kinzinger of Illinois.

On Sunday, Kinzinger asked on NBC: “What did the president know about 6 January leading up to 6 January?

“It’s the difference between, was the president absolutely incompetent or a coward on 6 January when he didn’t do anything or did he know what was coming? That’s a difference between incompetence with your oath and possibly criminal.”

On Sunday night, a spokesperson said the committee would respond to Jordan soon and “consider appropriate next steps”.

“Mr Jordan has admitted that he spoke directly to President Trump on 6 January and is thus a material witness,” the spokesperson said. “Mr Jordan’s letter to the committee fails to address these facts.”