The White House blocked the testimony of former senior adviser Rob Porter before the House Judiciary Committee on Tuesday, arguing that presidential aides are immune from subpoenas issued regarding their service in the administration.

Porter, a former chief of staff to Sen. Orrin Hatch and top aide to Sen. Mike Lee, was subpoenaed to appear before the committee in a hearing titled “Presidential Obstruction of Justice and Abuse of Power,” part of a series of efforts the Democratic-led panel is pursuing to dig into the findings of special counsel Robert Mueller that eventually could lead to impeachment proceedings.

Porter served as the White House staff secretary — a role that put him in the Oval Office nearly daily and in close contact with the president. He was a key source in Mueller’s report that showed repeated attempts by the president to hinder the investigation.

While the White House allowed former Trump campaign manager Corey Lewandowski to testify Tuesday under limited circumstances, it said Porter and former deputy chief of staff Rick Dearborn could not appear.

With regard to Porter, Assistant Attorney General Steven Engel wrote the Judiciary Committee that, “We conclude that he is absolutely immune from compelled congressional testimony in his capacity as former senior adviser to the president.”

Engel said that long-standing Justice Department policy says Congress cannot force senior advisers to testify about their official duties because it could cause a chilling effect on discussions the president needs to have with his senior staff.

“Because the president’s closest advisers serve as his alter egos, compelling them to testify would undercut the ‘independence and autonomy’ of the presidency ... and interfere directly with the president’s ability to faithfully discharge his responsibilities,” Engel wrote.

Porter resigned from the White House in February 2018 after his two ex-wives alleged he had abused them — accusations that Porter denies.

“It is inconsequential that Mr. Porter is now a private citizen,” Engel wrote the committee.

White House counsel Pat Cipollone cited the Justice Department letter in informing the committee that Porter and Dearborn would not appear.

“The long-standing principle of immunity for senior advisers to the president is firmly rooted in the Constitution's separation of powers and protects the core functions of the presidency,” Cipollone wrote. “We are adhering to this well-established precedent in order to ensure that future presidents can effectively execute the responsibilities of the Office of the President.”

Porter on Tuesday referred questions to his attorney, Brant Bishop.

“Mr. Porter is currently under conflicting and contradictory directives from two coequal branches: Congress has instructed him to testify and the president has instructed him not to do so,” Bishop said in a statement.

“Mr. Porter’s absence today reflects his respect for the constitutional responsibilities of all three branches of the federal government in resolving this conflict,” Bishop continued. “Congress and the president may reach an accommodation, or the Judiciary [branch] may resolve the conflict in the courts.”

When this conflict is resolved, Bishop said, Porter will “fulfill his duty, whether that means to provide appropriate testimony or to uphold the prerogatives of the Office of the Presidency.”

Bishop noted that Porter answered every question asked of him by the special counsel during nearly 20 hours of interviews.

House Judiciary Committee Chairman Jerry Nadler, D-N.Y., disputed the White House's assertions that Porter and Dearborn couldn't testify and decried limits placed on Lewandowski, who actually never worked for the White House.

“This is a shocking and dangerous assertion of executive privilege and absolute immunity,” Nadler said Tuesday. “The president would have us believe that he can willfully engage in criminal activity and prevent witnesses from testifying before Congress — even if they did not actually work for him or his administration. If he were to prevail in this cover-up while the Judiciary Committee is considering whether to recommend articles of impeachment, he would upend the separation of powers as envisioned by our founders.

“No one is above the law,” Nadler continued. “The House Judiciary Committee will continue our investigation of the president’s crimes, corruption and cover-up and get to the truth for the American people.”

Porter, who earned his bachelor’s degree from Brigham Young University and a master’s from Harvard, was cited multiple times in Mueller’s extensive report.

The special counsel says that Trump at one point directed Porter to tell White House counsel Don McGahn to create a false record saying Trump had never ordered him to fire Mueller as special counsel. Porter relayed the message but McGahn refused the order.

At another time, Trump was angered that then-Attorney General Jeff Sessions had recused himself from the probe of Russia’s 2016 election interference — and whether Trump’s team was connected — and told Porter to ask a top Justice Department official to take over supervision of Mueller’s office. Porter refused.

Porter's role in overseeing the nerve center of the White House ended after reports surfaced that his ex-wives had said he abused them.

His first wife, Colbie Holderness, told the Daily Mail that Porter was “verbally, emotionally and physically abusive and that’s why I left.” She produced a photo of her with a blackened eye.

His second wife, Jennifer Willoughby, told the British publication that Porter was abusive and that she was “walking on eggshells” during their marriage because of his anger.

Porter has denied the allegations, calling them “vile claims” and that the the truth is “nowhere close to what is being described.”