The U.S. House Intelligence Committee's impeachment inquiry report is taking direct aim at White House counsel Pat Cipollone's legal claims behind the president's refusal to participate in the impeachment proceedings, warning they could do lasting damage to Congress' ability to investigate potential abuses of power.

In the report, released Tuesday, congressional investigators said the letter "advanced remarkably politicized arguments and legal theories unsupported by the Constitution, judicial precedent, and more than 200 years of history."

"If allowed to stand, the President's defiance, as justified by Mr. Cipollone, would represent an existential threat to the nation's Constitutional system of checks and balances, separation of powers, and rule of law," the report reads.

The White House counsel's letter, as noted in the report, was met with widespread and bipartisan criticism in the legal community.

That criticism only deepened with the release of Tuesday's report, which characterized Trump's stonewalling as being a dire threat to the House's impeachment powers.

"If left unanswered, President Trump's ongoing effort to thwart Congress' impeachment power risks doing grave harm to the institution of Congress, the balance of power between our branches of government, and the Constitutional order that the President and every Member of Congress have sworn to protect and defend," the document reads.

The authors offered a nearly point-by-point rebuttal of Cipollone's legal claims. For example, the report takes on the White House attorney's assertion that "it is unconstitutional to exclude agency counsel from participating in congressional depositions."

"Mr. Cipollone cites no case law to support his position—because there is none," the report states. "Instead, he relies on a single opinion from the Trump Administration's Office of Legal Counsel and ignores the ample legal authority and historical precedent that clearly support the Committees' actions."

And in response to Cipollone's claims that Trump's top advisers are "absolutely immune" from having to testify before Congress, the House report points to court rulings striking down the concept.

"In ordering categorical defiance of House subpoenas, President Trump has confirmed the unlimited breadth of his position and his unprecedented view that no branch of government—even the House—is empowered to investigate whether he may have committed constitutional offenses," the report reads.

Cipollone has played a prominent role in defending the president in the course of the inquiry. He has been in touch with Republican senators ahead of an anticipated Senate trial early next year, and has been the attorney responding to the House's efforts, rather than any of Trump's private lawyers.

And Cipollone, a former partner at Kirkland & Ellis and Stein, Mitchell, Cipollone, Beato & Missner, on Sunday again called the inquiry "baseless and highly partisan" in a letter to House Judiciary Committee Chairman Jerry Nadler.

In that letter, Cipollone said the White House won't participate in the Judiciary Committee's first impeachment hearing Wednesday, but left the door open to it engaging in future proceedings.

The second half of Tuesday's report focuses on Trump's efforts to obstruct the impeachment inquiry, largely by refusing to provide documents or allow top administration officials to testify as part of the probe.

It lists each witness who was called to testify and then defied the subpoena at the direction of the administration. Some of those witnesses pointed to Cipollone's letter as a reason not to comply with the subpoena.

But, as the report notes, several witnesses still complied with subpoenas and testified both at closed-door depositions and public hearings.

"These officials not only served their nation honorably, but they fulfilled their oath to support and defend the Constitution of the United States," the report reads.

The report also points to ongoing Freedom of Information Act litigation for documents related to the Ukraine investigation. It specifically cited documents obtained by the watchdog group American Oversight last month, which included emails between Trump's personal attorney Rudy Giuliani and State Department officials, including Secretary of State Mike Pompeo, in relation to Ukraine.

"This handful of documents was limited to a narrow window of time and specific people, but it clearly indicates that the Department is withholding documents that are responsive to the Committees' requests," the report reads.

Read more: