Horowitz is the chairperson and Lerner is the vice chairperson of the council. More than five dozen other inspectors general also signed their letter to Engel, who heads the Justice Department’s OLC.

The whistleblower complaint, lodged by an anonymous intelligence official in August, detailed President Donald Trump’s July phone call with Ukrainian President Volodymyr Zelensky and alleged efforts by White House officials to “lock down” records of the conversation.

Michael Atkinson, the intelligence community’s inspector general, deemed the complaint credible and “urgent,” and forwarded the document to acting Director of National Intelligence Joseph Maguire, who initially refused to provide it to Congress.

Maguire acknowledged during testimony before the House Intelligence Committee in September that he first discussed the complaint with the White House counsel’s office, and then consulted with the Justice Department’s OLC — which concluded the complaint did not meet the legal definition of “urgent” because Trump is not an employee of the intelligence community.

But Atkinson disagreed with the OLC opinion and informed the House Intelligence Committee of the complaint’s existence. The “arguments and concerns” he raised in his response to the OLC memorandum were “compelling,” Horowitz and Lerner wrote.

“In this matter, OLC did not find that production to Congress was limited due to a valid constitutional concern,” they wrote. “Rather, OLC substituted its judgment and reversed a determination the statute specifically entrusted to the ICIG because of its independence, objectivity, and expertise to credibly assess the information.”

Maguire eventually turned the complaint over to Congress after significant pressure from lawmakers including a threat by House Intelligence Chairman Adam Schiff (D-Calif.) to pursue legal action against the administration.

Horowitz and Lerner also warned in their letter “that the OLC opinion creates uncertainty for federal employees and contractors across government about the scope of whistleblower protections, thereby chilling whistleblower disclosures.”

They concluded: “We urge you to reconsider the conclusions of the OLC opinion and withdraw or modify it.”

The president and his allies have dismissed the whistleblower as a partisan with no first-hand knowledge of the events in question.

“Where is the Whistleblower, and why did he or she write such a fictitious and incorrect account of my phone call with the Ukrainian President?,” Trump tweeted Thursday. “Why did the IG allow this to happen? Who is the so-called Informant (Schiff?) who was so inaccurate? A giant Scam!”

Lawyers for the whistleblower, Andrew Bakaj and Mark Zaid, have pushed back on the president's characterization of their client's complaint. In an opinion article published Friday, they argued, “the reality is that the identity of the whistleblower is irrelevant” because his account has been largely corroborated.

The Justice Department responded on Friday in a letter, stating that it is the "sole responsibility" of the DOJ to interpret the statutes as Congress has written them, and they did "precisely that" in their opinion.

"We are confident that our opinion does not diminish the statutory protections that Congress has provided to federal employees and contractors who make good-faith disclosures to inspectors general," wrote Assistant Attorney General Steven Engel.