Declaring the Democratic-led impeachment inquiry illegitimate, Vice President Mike Pence and President Donald Trump's personal lawyer Rudy Giuliani on Tuesday refused to hand over documents on Ukraine.
The Defense Department and White House's Office of Management and Budget also declined to comply with the investigation, defying congressional subpoenas, officials said.
The move dramatically escalates the standoff between the Democratic-led House and the White House, which also has told administration officials not to testify and has otherwise stonewalled Congress.
"If they enforce it, then we will see what happens," Giuliani said of his congressional subpoena.
(MORE: Democratic chairmen subpoena Giuliani for documents in impeachment probe )Trump and his supporters say the inquiry isn't legitimate because House Speaker Nancy Pelosi initiated impeachment without a formal vote. They note that in the cases of Presidents Richard Nixon and Bill Clinton, the House held initial votes on whether to proceed.
Democrats have insisted that a vote isn't necessary for an inquiry ahead of more formal impeachment proceedings. House Speaker Nancy Pelosi on Tuesday stood by that decision, at least for now, telling reporters that Republicans couldn't defend Trump so they were attacking the process.
Rep. Adam Schiff, the Democratic chairman of the Intelligence Committee, said the House would stay focused on gathering information.
"The evidence of obstruction of Congress continues to mount," he told reporters. "We are nonetheless continuing to get good and important information from witnesses."
(MORE: Pelosi, Schiff defend impeachment probe, lack of formal floor vote )While Giuliani was given a wide-ranging subpoena by Democrats, Pence's office was asked to provide Congress with certain documents.
In a statement released late Tuesday, Pence's office said it would only cooperate if Congress returned to the "regular order of legitimate legislative oversight requests."
(MORE: Rudy Giuliani's relationship with arrested men is subject of criminal investigation: Sources)"Until that time, the Office of the Vice President will continue to reserve all rights and privileges that may apply, including those protecting executive privileges, national security, attorney-client communications, deliberations, and communications among the President, the Vice President, and their advisors," Pence's office stated.
The House is investigating a whistleblower complaint that Trump pressed Ukraine to investigate his political rival Joe Biden and Biden's son. Giuliani has emerged as a central figure in the inquiry, pressing repeatedly a discredited theory that corrupt Ukrainian politicians meddled in the 2016 elections and were trying to help Democrat Hillary Clinton.
U.S. intelligence officials say it was Russia, not Ukraine, that orchestrated election interference and in favor of Trump, not Clinton.
Pence and Giuliani also have defended the push for Ukraine to investigate the Bidens. In an interview with ABC News, Hunter Biden denied any wrongdoing by engaging in foreign work but acknowledged "poor judgement" by failing to take into account his father's position as vice president.
(MORE: Hunter Biden sits down for exclusive interview with ABC News)Tuesday was the deadline for Giuliani to comply with a wide-ranging subpoena from three of the House committees working on the impeachment inquiry.
"A growing public record indicates that the President, his agent Rudy Giuliani, and others appear to have pressed the Ukrainian government to pursue two politically-motivated investigations," the Democratic chairmen wrote. "The Committees have reason to believe that you have information and documents relevant to these matters."
(MORE: Rudy Giuliani fires back at former White House aide who accused him of spreading ‘completely false' theory )Giuliani had previously told ABC News Chief Anchor George Stephanopoulos that he would "consider" cooperating with the congressional request but only if his client -- the president -- signed off.
"I'm a lawyer. It's his privilege, not mine," Giuliani told ABC News last month. "If he decides that he wants me to testify, of course I'll testify, even though I think Adam Schiff is an illegitimate chairman. He has already prejudged the case."
(MORE: 2 men with ties to Giuliani arrested on campaign finance charges, bond set at $1M )Separately, Giuliani said Tuesday that he is no longer retaining the services of Jon Sale, who was acting as his attorney for this matter. Giuliani said that if Congress seeks to enforce a subpoena, then he will retain counsel.
As part of his final acts as his attorney, Sale sent a letter to Congress on Tuesday replying to the subpoena Giuliani was sent.
ABC News reporter Benjamin Siegel and Luis Martinez contributed to this report.