The White House said Tuesday that it will not cooperate with House Democrats' impeachment inquiry into President Donald Trump, claiming that the proceedings amount to "baseless, unconstitutional efforts to overturn the democratic process."
"You have designed and implemented your inquiry in a manner that violates fundamental fairness and constitutionally mandated due process," White House counsel Pat Cipollone said in an eight-page letter to House Speaker Nancy Pelosi, House Intelligence Chairman Adam Schiff, Oversight Chairman Elijah Cummings and Foreign Affairs Chairman Eliot Engel.
"Put simply, you seek to overturn the results of the 2016 election and deprive the American people of the President they have freely chosen," Cipollone added.
He also accused the Democratic leaders of viewing the impeachment inquiry as "a means to undo the democratic results of the last election, but as a strategy to influence the next election" in 2020.
A senior White House official told CNBC's Eamon Javers that the letter signifies a "full halt" to cooperation with the impeachment inquiry.
Dozens of Democrats were spurred to support an impeachment inquiry after learning of damning allegations in a whistleblower's complaint, which accused Trump of "using the power of his office to solicit interference from a foreign country in the 2020 U.S. election."
That complaint focused mainly on Trump's July 25 phone call with Ukrainian President Volodymyr Zelensky, a partial transcript of which was released by the White House late last month. In that call, Trump asked Ukraine to "look into" unsubstantiated corruption allegations against former Vice President Joe Biden — a front-runner in the Democratic presidential primary — and his son Hunter.
Trump also asked Zelensky to "do us a favor though" and investigate matters related to the Russia probe concluded earlier this year by former special counsel Robert Mueller, after the Ukraine leader said his administration was "almost ready to buy more [Javelin missiles] from the United States for defense purposes."
That exchange, and the White House's decision to delay hundreds of millions of dollars in military aid to Ukraine, have raised suspicions among Democrats that Trump was trying to pressure a foreign leader to investigate his potential political opponents. The aid, which was delayed for months without a clear explanation, was ultimately given to Ukraine last month.
Cipollone's fiery letter came hours after the White House blocked a key witness in the impeachment probe from testifying behind closed doors before the House panels. The State Department directed that official, U.S. Ambassador to the European Union Gordon Sondland, not to show up for the meeting.
Schiff called the Trump administration's moves "acts of obstruction of a coequal branch of government," and added that Sondland had also been blocked from sharing documents in his possession related to the inquiry.
The Democratic leaders subpoenaed Sondland to testify and produce documents later Tuesday evening.
In a statement, White House press secretary Stephanie Grisham said, "The President has done nothing wrong, and the Democrats know it."
"These partisan proceedings are an affront to the Constitution — as they are being held behind closed doors and deny the President the right to call witnesses, to cross-examine witnesses, to have access to evidence, and many other basic rights," Grisham said.
Cipollone's letter strikes a defiant tone from the outset, excoriating Democrats' "legally unsupported demands made as part of what you have labeled — contrary to the Constitution of the United States and all past bipartisan precedent — as an 'impeachment inquiry.'"
"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," Cipollone wrote.
The White House counsel asks the Democratic leaders to "abandon the current invalid efforts to pursue an impeachment inquiry" in light of "the many deficiencies we have identified in your proceedings."
Cipollone highlights a litany of alleged offenses by the Democrats. The probe violates due process rights, he contends, because the House has yet to take "political accountability ... by voting to authorize" an impeachment inquiry. He also claims the Democrats have "abandoned" any due process protections for Trump himself.
"No citizen — including the President — should be treated this unfairly," Cipollone writes.
Schiff, who has faced the brunt of Trump's criticism in the impeachment inquiry thus far, was the first of the Democratic leaders to respond to the letter.
"They say: they will not cooperate with an impeachment inquiry unless it's on their terms. They mean: the President is above the law," Schiff tweeted.
"The Constitution says otherwise."
Read the full letter below: