The Trump administration is committing "an unprecedented level of stonewalling, delay and obstruction" in response to congressional requests for documents and witnesses, the chair of the House oversight committee has said.
Elijah Cummings, Democratic congressman for Maryland, said he had sent 12 letters to the White House on a range of topics from the "routine" to "relating to our core national security interests".
In an op-ed for The Washington Post, Mr Cummings said the subjects included White House security clearances, Donald Trump's alleged hush money payments, and the use of taxpayer funds for lavish private planes.
The Trump administration "has not turned over a single piece of paper to our committee or made a single official available for testimony," Mr Cummings wrote.
The administration has also ignored requests by three inquiries into the administration by the House judiciary committee, which has impeachment jurisdiction.
The White House considers the requests by newly empowered Democrats- who took the House in November - as illegitimate, too expansive or infringing on presidential privilege, the Post reported.
Administration sources told the newspaper it planned to challenge the majority of document requests.
But Democrats say the White House is trying to thwart Congress's fundamental oversight role of the executive.
"Trump's actions violate our Constitution's fundamental principle of checks and balances," Mr Cummings wrote.
The Trump administration is expected to draft an official response over its failure to comply with the request some time in the next week.
If it continues to refuse, Democrats could sue the administration and ultimately take officials to court, where it could get caught up in litigation for years.
The House judiciary committee is probing whether Mr Trump abused his power as president, obstructed justice, or engaged in corruption, while the oversight committee is looking into issues including the president's hush money payments to two women and his handling of security clearances.
Additional reporting by AP