(CNN) The House Intelligence Committee is accusing former White House national security adviser Michael Flynn of failing to comply with its subpoena as part of its Russia investigation.
The committee is now demanding that Flynn appear on September 25 and provide documents by September 18, according to a letter Chairman Adam Schiff, a Democrat from California, sent to Flynn on Friday.
Flynn pleaded guilty to lying to the FBI in former special counsel Robert Mueller's investigation back in 2017, but he is still awaiting sentencing. Flynn had long been a cooperating witness for the government since his guilty plea, but earlier this year Flynn obtained a new legal team and has accused federal prosecutors of withholding significant documents and audio recordings related to his criminal charge and the Mueller investigation.
The committee says that Flynn's cooperation with the government should extend to cooperating with Congress, but he has not done so.
"General Flynn and his counsel have failed to cooperate with the Committee in all respects — he has provided no documents in response to our subpoena, nor has he engaged with the Committee in an appropriate or satisfactory manner," a committee staffer said. "General Flynn agreed to cooperate with the United States government, which should include the Congress. And while we cannot evaluate whether he has met his obligation to the Justice Department, there is no question that he has thus far failed to cooperate with the Congress in any meaningful way."
An attorney for Flynn, Sidney Powell declined to comment on Schiff's latest letter, but provided CNN her previous correspondence with the committee, in which she pointed to Flynn's previous document production to Congress and accused the committee of making "unreasonable and unethical" demands that Flynn appear if he planned to invoke his Fifth Amendment privilege.
"We have already informed you that at our insistence, Mr. Flynn will assert his Fifth Amendment privilege and will not answer any questions. He remains, after all, a defendant in a criminal prosecution that has not been concluded," Powell wrote in an August letter. "Your demand that he appear at a hearing merely to assert the privilege against self-incrimination is transparently pure harassment, because it cannot achieve any legitimate congressional purpose."
In the letter to Flynn, Schiff said that Powell told the committee Flynn was "not in a position to testify" until his criminal charges were resolved and that if he was called he "will invoke the Fifth Amendment."
Schiff responded that Flynn's "blanket invocation of the Fifth Amendment" was inadequate without having discussed potential topics that would be asked.
Flynn's fight with the committee comes as his lawyers last month claimed that federal prosecutors have withheld evidence related to Flynn's criminal case. The court filing leaned into conspiracy theories of investigators' misconduct, accusing prosecutors of suppressing evidence and highlighting contacts that Mueller's team had with Peter Strzok, Lisa Page and Bruce Ohr.
Prosecutors say Flynn could be sentenced in October or November, and a status hearing for his case is scheduled for Tuesday.
This story has been updated with additional developments Monday.