Biden accuses Trump and his allies of holding ‘a dagger at the throat of America.’

President Biden forcefully denounced former President Donald J. Trump for promoting lies and tearing down democracy because he could not stand the fact that he lost a free and fair election, accusing his predecessor and his allies of holding “a dagger at the throat of America.”

In his most sustained and scathing attack on the former president since taking office, Mr. Biden used the anniversary of the Jan. 6 mob assault on the Capitol to condemn Mr. Trump for waging an “undemocratic” and “un-American” campaign against the legitimacy of the election system that he likened to the actions of autocrats and dictators in faraway countries.

“The former president of the United States of America has created and spread a web of lies about the 2020 election,” Mr. Biden said, standing in the same National Statuary Hall invaded by throngs of Trump supporters a year ago. “He’s done so because he values power over principle, because he sees his own interests as more important than his country’s interests and America’s interests, and because his bruised ego matters more to him than our democracy or our Constitution. He can’t accept he lost.”