Former national security advisor Michael Flynn says he's refusing to turn over records to the Senate Intelligence Committee because of the "escalating public frenzy" surrounding the investigation, according to The Associated Press.

The news service obtained a letter sent to the committee blaming Flynn's decision not to cooperate on the "escalating public frenzy" around the investigation into ties between President Trump's campaign and Russian officials. The Justice Department's appointment of a special counsel to oversee the investigation is also mentioned.

The letter, sent to the committee by Flynn's lawyers, says that the former national security advisor is invoking his Fifth Amendment rights and refusing to testify because "any testimony he provides could be used against him," according to the AP.

Earlier Monday, the AP reported that Flynn will refuse to comply with a Senate Intelligence Committee subpoena and will invoke his Fifth Amendment rights.

Flynn previously offered to testify before the Senate and House intelligence committees in exchange for immunity, but neither panel accepted his offer.

He was fired from his post as national security advisor in February for misleading Vice President Mike Pence and other White House officials about conversations with Russian Ambassador Sergey Kislyak. Russian officials reportedly bragged during the 2016 campaign that they could use Flynn to influence Trump in the White House.

Flynn has come under scrutiny for lobbying work he did on behalf of the Turkish government during last year's election. He reportedly pushed to delay an attack plan against the Islamic State in Iraq and Syria that Turkey opposed during Trump's transition.