Agencies critical to US security have suffered “enormous damage” at the hands of the Trump administration, US President-elect Joe Biden has said.
Mr Biden said his team was not getting the information it needed, including from the Department of Defense, as it makes its transition to power.
He spoke after a briefing by national security and foreign policy aides.
Mr Biden takes office on 20 January but President Donald Trump has refused to accept defeat in November’s election.
For weeks after the 3 November election, Mr Biden was blocked from receiving key intelligence briefings, an essential and normally routine part of a presidential transition.
Following Mr Biden’s remarks on Monday, Acting Defense Secretary Christopher Miller said officials had been “working with the utmost professionalism to support transition activities”.
“The Department of Defense has conducted 164 interviews with over 400 officials and provided over 5,000 pages of documents – far more than initially requested by Biden’s transition team,” he said.
A spokesman said the Pentagon had been “completely transparent” with the Biden team.
In a speech following a video conference call with advisers which he posted on Twitter, Mr Biden said his team was facing “roadblocks” in the Department of Defense and the Office of Management and Budget.
“Right now, we just aren’t getting all the information that we need from the outgoing administration in key national security areas,” he said.
“It is nothing short, in my view, of irresponsibility.”
The president-elect added that his team needed a “clear picture of our force posture around the world” and that US adversaries could exploit any confusion that resulted.
He said: “Many of the agencies that are critical to our security have incurred enormous damage.
“Many of them have been hollowed out in personnel, capacity and in morale. The policy processes have atrophied or have been sidelined.”
Mr Trump sacked his Defence Secretary Mark Esper shortly after the election, apparently over Mr Esper’s disagreement with his call to deploy the military against anti-racism protesters.
Mr Trump’s subsequent installation of loyalists in the department was viewed with concern by political opponents, who saw it as an attempt to sow chaos in the final weeks of his administration.