Former national security adviser Mike Flynn's attorney has told the Senate Intelligence Committee that Flynn will invoke his Fifth Amendment rights, and will not respond to a subpoena for documents related to Flynn's work and contacts in Russia.

He also claimed that Flynn is the target "of outrageous allegations" that feed an "escalating public frenzy against him."

The letter from attorney Robert Kelner to Sens. Richard Burr, R-N.C., and Mark Warner, D-Va., said that Flynn is eager to "give a full account of the facts."

But it added: "Our client's position remains unchanged. Producing documents that fall within the subpoena's broad scope would be a testimonial act, insofar as it would confirm or deny the existence of such documents."

"The context in which the committee has called for General Flynn's testimonial production of documents makes clear that he has more than a reasonable apprehension that any testimony he provides could be used against him," Kelner added.

Last week, the Justice Department named a special counsel to examine all issues related to the Trump administrations' ties to Russia, which is expected to examine Flynn's contact with Russian officials. Senators who were briefed on the special counsel's duties said their impression was that the special counsel, former FBI Director Robert Mueller, could be looking at criminal penalties.

However, the letter made few references to the new special counsel, which is noteworthy because some lawmakers worried that the appointment of a special counsel could lead to numerous potential witnesses using their Fifth Amendment rights.

The committee issued the subpoena to Flynn just one day after President Trump abruptly fired James Comey as the director of the FBI, which ultimately led to the political pressures that caused the Justice Department to create the special counsel.

Flynn was already of interest to the Intelligence Committee after he failed to disclose money he earned from an appearance at a Russian-sponsored television station. But he was of even greater interest when details of a memo written by Comey were leaked in the media last week. The Comey memo is said to detail a private meeting between Trump and Comey just one day after Flynn was fired, and Trump allegedly told Comey, "I hope you can let this go."

Flynn was fired from his duties as national security advisor because before the Trump administration was sworn in, Flynn spoke with Russian Ambassador Sergei Kislyak about the sanctions placed on Russia by the Obama administration for Russia's interference with the 2016 elections. Flynn told administration officials, including Vice President Mike Pence, he had not discussed sanctions. However, a transcript of the call, which was intercepted by U.S. foreign surveillance activities, was leaked to the press showing otherwise.

Flynn also reportedly sought to provide his testimony to both the House and Senate Intelligence Committees in exchange for immunity, according to a media report that broke in late March. Neither committee accepted the offer.