White House officials announced Tuesday they will refuse to cooperate with the House impeachment inquiry focused on President Donald Trump’s request that Ukraine’s president investigate Joe Biden and son Hunter.

The move amounts to the latest escalation in the three-week-old impeachment saga, with the White House arguing Speaker Nancy Pelosi has set up a “legally unsupported” probe by opting against holding a floor vote on whether to launch a formal impeachment inquiry.

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“As you know, you have designed and implemented your inquiry in a manner that violates fundamental fairness and constitutionally mandated due process,” White House Counsel Pat Cipollone wrote in a letter to Pelosi and three committee chairmen involved in the impeachment probe. “Put simply, you seek to overturn the results of the 2016 election and deprive the American people of the President they have freely chosen. … Your highly partisan and unconstitutional effort threatens grave and lasting damage to our democratic institutions, to our system of free elections, and to the American people.

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“For example, you have denied the President the right to cross-examine witnesses, to call witnesses, to receive transcripts of testimony, to have access to evidence, to have counsel present, and many other basic rights guaranteed to all Americans. You have conducted your proceedings in secret,” Cipollone wrote. “You have violated civil liberties and the separation of powers by threatening Executive Branch officials, claiming that you will seek to punish those who exercise fundamental constitutional rights and prerogatives.”

The letter continues: “All of this violates the Constitution, the rule of law, and every past precedent. Never before in our history has the House of Representatives-under the control of either political party-taken the American people down the dangerous path you seem determined to pursue.”

Trump was asked about the impeachment drama during an unrelated event in the Oval Office minutes after the White House released the letter. He did not respond to reporters’ questions, however.

In recent days, top White House officials — including the president — and his outside surrogates have latched onto an argument top House Republicans began making shortly after Pelosi on Sept. 24 announced the House Intelligence Committee would lead an impeachment investigation.

“Adam Schiff and Speaker Pelosi are intentionally skirting prior impeachment precedent in order to deny Republicans basic rights in their partisan investigation,” House Foreign Affairs ranking member Michael McCaul, R-Texas, said earlier Tuesday in a statement. “In the Nixon and Clinton [impeachment] cases, votes were taken on the House floor to establish a formal inquiry which set up the rules of the road.

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“Today, Democrats have denied House members the opportunity to take that vote,” he said. “Their rush to impeachment has ensured there will be no fairness in this process and is reckless when the presidential election is 13 months away.”

But the speaker has contended since she announced the inquiry that there is no legal or institutional requirement that would make a floor vote necessary.

“The existing rules of the House provide House Committees with full authority to conduct investigations for all matters under their jurisdiction, including impeachment investigations,” she wrote in an Oct. 3 letter to House Minority Leader Kevin McCarthy, R-Calif. “There is no requirement under the Constitution, under House Rules, or House precedent that the whole House vote before proceeding with an impeachment inquiry.”

But Cipollone informed the senior House Democrats that the administration will “reject your baseless, unconstitutional efforts to overturn the democratic process.”

“Your unprecedented actions have left the President with no choice,” the top White House lawyer wrote. “In order to fulfill his duties to the American people, the Constitution, the Executive Branch, and all future occupants of the Office of the Presidency, President Trump and his Administration cannot participate in your partisan and unconstitutional inquiry under these circumstances.”

Another reason the White House opted to resist the inquiry relates to reports House Intelligence Chairman Adam B. Schiff of California had contact with a whistleblower who raised concerns about Trump’s call with the Ukrainian leader before that person formally raised alarms to the intelligence community inspector general.

Cipollone told Pelosi and the chairmen that Schiff acted to “covertly assist with the submission of a complaint, mislead the public about his involvement, read a counterfeit version of the call to the American people, and then pretend to sit in judgment as a neutral ‘investigator.’”

“These are questions that ought to be explored … but there is not opportunity for the president or the minority in the House to explore them,” a senior administration official told reporters on a briefing call. “The entire process is flawed from the outset.”

Schiff and other Democrats earlier in the day contended any refusal by the White House to cooperate with the probe would amount to obstruction of justice. The senior administration official, however, called the move constitutional because it was partially based on the president’s right to due process.

“Congress can’t have it both ways” because traditional oversight is a different authority than holding a formal impeachment inquiry, the official said.