Lawyers representing the whistleblower behind the explosive complaint involving 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's efforts to persuade Ukraine’s president to investigate former Vice President Joe Biden and his son Hunter Biden expressed concern for their client's safety in a letter to lawmakers released Sunday.

In a letter to Senate Intelligence Committee Chairman Richard Burr Richard Mauze BurrHillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Bipartisan representatives demand answers on expired surveillance programs Rep. Mark Walker says he's been contacted about Liberty University vacancy MORE (R-N.C.), House Intelligence Committee Chairman Adam Schiff Adam Bennett SchiffSchiff to subpoena top DHS official, alleges whistleblower deposition is being stonewalled Schiff claims DHS is blocking whistleblower's access to records before testimony GOP lawmakers distance themselves from Trump comments on transfer of power MORE (D-Calif.) and others, lawyers representing the whistleblower said they had "serious concerns for our client’s personal safety, as well as for others connected to this matter." They called on lawmakers "to speak out in favor of whistleblower protection and reiterate that this is a protected system where retaliation is not permitted, whether direct or implied."

The lawyers also attached correspondence with acting Director of National Intelligence Joseph Maguire Joseph MaguireCongressional Democrats request FBI briefing on foreign election interference efforts Wells Fargo told employees to delete TikTok from work phones Hillicon Valley: Pompeo floats TikTok ban | Civil rights groups slam Facebook after call | Election security funding included in proposal MORE thanking him for his supportive words during his testimony and expressing concerns for their client.

"60 Minutes," which first obtained the letter, originally reported that the contents suggested the whistleblower was under federal protection. However, lawyer Mark Zaid said in a statement to The Hill that the news outlet "completely misinterpreted the contents of our letter."

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The whistleblower's complaint, which was released to the public on Thursday, is at the center of House Democrats' impeachment inquiry.

Trump and his allies have sought to discredit the complaint and the whistleblower behind it.

The president on Sunday tweeted that the person who filed the complaint should be outed and that they will face "Big Consequences."

Little is known about the whistleblower, who, according to the complaint, was not a direct witness to the conversation but was told about it by White House colleagues.

The president's camp has zeroed in on the whistleblower not being directly privy to the call between Trump and his Ukrainian counterpart, Volodymyr Zelensky, as a disqualification of the complaint.

The partial transcript of the call confirms the whistleblower's claim that Trump pressed Zelensky to investigate the Biden family.

The New York Times has reported the whistleblower is a CIA officer who is currently working at the agency's headquarters in Langley, Va.

EDITOR'S NOTE: This story has been updated with a statement from the lawyer and to clarify the contents of the letter.