Former attorney general William Barr said President Donald Trump’s conduct as a violent mob of his supporters stormed the US Capitol was a “betrayal of his office and supporters”.
In a statement, Mr Barr said that “orchestrating a mob to pressure Congress is inexcusable”.
Mr Barr was one of Mr Trump’s most loyal and ardent defenders in the Cabinet.
His comments come a day after angry and armed protesters broke into the US Capitol, forcing Congress members to halt the ongoing vote to certify President-elect Joe Biden’s election and then flee from the House and Senate chambers.
Mr Barr resigned last month amid lingering tension over the president’s baseless claims of election fraud and the investigation into Mr Biden’s son.