The US House of Representatives committee investigating the January 6 Capitol insurrection subpoenaed former White House counsel Pat Cipollone to give evidence about former president Donald Trump's movements on the day of the attack.
The subpoena was announced days after a former top White House aide said that Mr Cipollone had warned her the administration could be charged with “every crime imaginable” if the president joined the armed rioters outside the steps of the Capitol.
“The Select Committee's investigation has revealed evidence that Mr Cipollone repeatedly raised legal and other concerns about President Trump’s activities on January 6 and in the days that preceded,” the panel said in a statement on Wednesday.
“Any concerns Mr Cipollone has about the institutional prerogatives of the office he previously held are clearly outweighed by the need for his testimony.”
The evidence given by Cassidy Hutchinson, who served as aide to former White House chief of staff Mark Meadows, marked the second time Mr Cipollone's name was brought up during the public hearings.
Three former Justice Department officials stated that mid-level lawyer Jeffrey Clark drafted a letter that would have urged the US state of Georgia to appoint a new slate of electors that would declare Mr Trump had won the state in the 2020 presidential elections.
One White House lawyer recalled Mr Cipollone refusing to sign it, calling the letter a “murder-suicide pact”.
Mr Cipollone and the Justice Department officials threatened to resign en masse during a meeting on January 4, 2021, when Mr Trump considered appointing Mr Clark — who embraced Mr Trump's claims of voter fraud — as acting attorney general.
Committee vice chairwoman Liz Cheney said Mr Trump's actions leading up to and on January 6 were far more “chilling” than previously imagined.
“We are confronting a domestic threat that we have never faced before. And that is a former president who is attempting to unravel the foundations of our constitutional republic,” she said in remarks at the Ronald Reagan Presidential Library on Wednesday night.
“As the full picture is coming into view with the January 6 committee, it has become clear that the efforts Donald Trump oversaw and engaged in were even more chilling and more threatening than we could have imagined.”
Ms Cheney said that Republicans cannot be loyal both to Mr Trump and the US Constitution.
A rare voice of dissent against Mr Trump in Congress, Ms Cheney has become a pariah within the Republican party, which has stripped her of her leadership positions and censured her in her home state of Wyoming.
She also faces a challenging primary campaign in which she currently trails Trump-backed challenger Harriet Hageman in the polls.
Reuters contributed to this report