The House speaker, Democrat Nancy Pelosi, announced on Wednesday that she would veto the two top Republicans appointed by the House minority leader, Kevin McCarthy, to the new select committee investigating the Capitol attack, saying the Trump-allied congressmen could threaten the integrity of the investigation.

But the move triggered McCarthy to pull all five of the Republicans he had chosen off the committee if Pelosi wouldn’t seat the whole cohort – and threaten to set up their own investigation into the 6 January Capitol attack.

With Pelosi refusing to back down and saying the committee would go ahead, the rejected Republicans said they considered that she had rejected all five.

The Republican House minority leader’s actions also spurred Liz Cheney, the lone Republican appointed to the committee by Pelosi and therefore not one of the five effectively withdrawn by McCarthy, to stand on the steps of the Capitol on Wednesday afternoon and decry his actions as “despicable and disgraceful”.