Trump was behind "incredibly damaging messages being sent to the rest of the world about how democracy functions," Biden said on Thursday.
He was talking to reporters in his home state of Delaware where he criticized the Trump administration’s refusal to give his team access to key federal agencies.
Biden argued the obstruction is affecting his team’s ability to create a plan to respond to the coronavirus pandemic, which has killed at least 252,000 Americans.
The former vice president has been projected by mainstream US media as the winner of the White House race.
Biden won the Electoral College votes by 306 to 232, flipping five states that went to Trump four years ago, according to the media.
Trump has rejected the call, and declared himself the winner.
He has also launched several lawsuits in a number of states, claiming election fraud.
Many of those suits have already failed, including one in Arizona, where a judge dismissed a Republican-backed lawsuit seeking to halt the certification of Biden as the winner of the state.
Trump also reportedly invited Michigan Republican lawmakers to the White House, after his campaign withdrew a federal lawsuit that called on the courts to block final certification of the results in Michigan, which Biden won by 155,000 votes.
Asked about the president’s calls with officials there, Biden said it was "another incident where he will go down in history as being one of the most irresponsible presidents in American history."
"It's hard to fathom how this man thinks," Biden said. "I'm confident he knows he hasn't won, is not going to be able to win and we're going to be sworn in January 20th."