The White House has ordered two former aides to President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE to defy their subpoenas to appear at a House Judiciary Committee hearing Tuesday.

White House counsel Pat Cipollone said in a letter to the panel that the Justice Department recommended and Trump directed Rick Dearborn and Rob Porter to go against their subpoenas due to "constitutional immunity."

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The letter said the two were told not to go “because of the constitutional immunity that protects senior advisers to the president from compelled congressional testimony, and in order to protect the prerogatives of the Office of President."

Democrats are legally objecting to the ability to declare "absolute immunity" in a suit against former White House counsel Don McGahn.

The only expected witness for Tuesday's hearing now is former Trump campaign manager Corey Lewandowski Corey R. LewandowskiTrump faces tricky choice on Supreme Court pick How Trump can win reelection: Focus on Democrats, not himself Trump Jr. distances from Bannon group, says he attended 'single' event MORE. Cipollone instructed Lewandowski in another letter that he should not disclose private conversations with the president beyond what is public from former special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's report, The Associated Press reported.

House Judiciary Committee Chairman Jerrold Nadler Jerrold (Jerry) Lewis NadlerDemocrats shoot down talk of expanding Supreme Court Schumer: 'Nothing is off the table' if GOP moves forward with Ginsburg replacement Top Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence MORE (D-N.Y.) subpoenaed all three to discuss what was reported by Mueller and to investigate whether Trump should be impeached.

Nadler said in a statement Monday night that the White House's directions are a "shocking and dangerous assertion."

“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,” Nadler said.