The speaker of the US House, Nancy Pelosi, intends to appoint a second anti-Trump Republican to the select committee which will investigate the deadly 6 January assault on the US Capitol by supporters of Donald Trump.

Asked if she would ask Adam Kinzinger of Illinois to join fellow Trump critic Liz Cheney of Wyoming on the panel, Pelosi told ABC’s This Week: “That would be my plan.”

Asked when the move would be formally announced, Pelosi said: “Perhaps after I speak to Adam Kinzinger. But … that is the direction that I would be going in.”

The committee is at the centre of high political drama. After the Republican House minority leader, Kevin McCarthy, named Jim Jordan and Jim Banks to the panel, both prominent allies of Donald Trump, Pelosi rejected them. McCarthy then withdrew Republican support, leaving in place only Cheney, a pariah in her party.

McCarthy was widely criticised. James Carville, a veteran Democratic strategist, went so far as to call him a “pathetic glob of protoplasm”, in thrall to Trump.

Pelosi said Kinzinger “and other Republicans have expressed an interest to serve on the select committee. And I wanted to appoint three of them that Leader McCarthy suggested. But he withdrew their names. The two that I would not appoint are people who would jeopardise the integrity of the investigation, and there’s no way I would tolerate their antics as we seek the truth.”

Asked about Republican charges that her rejection of Jordan and Banks worsened political divisions, Pelosi said: “This was not just any day of the week. This was a constitutionally required day of action for Congress.

“The Republicans will say what they will say. Our select committee will seek the truth. It’s our patriotic duty to do so … maybe the Republicans can’t handle the truth but we have a responsibility to seek it, to find it and in a way that retains the confidence of the American people.”

Speaking to Fox News Sunday, Banks, from Indiana, said: “It’s clear that Pelosi only wants members on this committee who will stick to her talking points and stick to her narrative. That’s why she’s picked the group that she’s already picked and anyone that she asks to be on this committee from this point moving forward will be stuck to her narrative, to her point of view. There won’t be another side.”

Banks repeatedly claimed he and Jordan were only concerned with finding out why security failed at the Capitol on 6 January.

Congress was attacked by Trump supporters told by the then president to “fight like hell” to overturn his election defeat.

Later that day, after rioters died and police officers were injured while protesters looked for lawmakers to capture and kill, Banks and Jordan went ahead with objections to results from Arizona and Pennsylvania.

Trump’s lie that his defeat by Joe Biden was the result of electoral fraud has been repeatedly debunked and thrown out of court. On Fox News Sunday, Banks was not asked about those claims, his support for them or how they fuelled the Capitol attack.

Elsewhere, a Republican senator who voted to impeach Trump over the Capitol attack and also backed an independent commission to investigate it repeated the talking point followed by Banks: that Democrats want the House committee to “drive a political message”.

“I think people do want to get to the bottom of [6 January],” Pat Toomey of Pennsylvania told CNN’s State of the Union.

“Yes, I did support the Senate version of a commission that would have been genuinely and truly bipartisan both in its composition of members, and in staff, which I think is important.”

Republicans in the Senate blocked that.

But, “this exercise in the House was not meant to be that … we have a lot of investigations under way now, there are Senate committees that have completed, there are others still in progress, we have many criminal investigations.

“I would favour a truly bipartisan commission. But I think that we should be candid about the fact that it is politically to the advantage of Democrats to try to keep this issue in the forefront. James Carville has been very candid about this, he’s urged the Democrats, ‘Don’t let the election be about Joe Biden and his policies in 2022, make that [midterm] election about 6 January and Donald Trump.

“And so it’s very clear that Democrats have an incentive to try to drive a political message here, and a purely partisan commission in the House is probably going to do that.”

Speaking on MSNBC this week, Carville said McCarthy, “the pathetic glob of protoplasm, he was panicked out of his mind on 6 January calling the president, begging for help. He refuses to have the bipartisan committee, now he’s doing this. The guy has no sense of shame.”

Toomey was asked if Republicans refusing to support a committee to investigate the actions of supporters of a Republican president might reflect badly on the party.

“No,” he said, “I think it is it is constant reminder about a terrible episode in our history, which Donald Trump was at the heart of, rather than looking at the policies of the current president which is more relevant in 2022, I would argue … and the damage that he’s going to be doing.

“That’s what we should be debating in 2022. But, you know, I’m not sure that’s what the Democrats want to be talking about.”