NEW YORK –

Former U.S. national security adviser Michael Flynn has hired Sidney Powell, a fierce critic of special counsel Robert Mueller's Russia investigation, as his new attorney, Powell's office said in a statement.

Powell, who has previously urged Flynn to withdraw his guilty plea over lying to the FBI www.reuters.com/article/us-usa-trump-russia/flynn-pleads-guilty-to-lying-on-russia-cooperates-with-u-s-probe-idUSKBN1DV50N about his contacts with Russia, suggested her client would not withdraw his plea and would adhere to the terms of his guilty plea signed in December 2017.

"Attorney Powell is honored to represent General Flynn and he will continue to cooperate with the government in all matters," the statement said.

The move comes about a week after Flynn fired two lawyers www.reuters.com/article/us-usa-trump-flynn/former-trump-adviser-flynn-shakes-up-legal-team-court-filing-idUSKCN1T723B who had represented him since before the Mueller probe started in May 2017, prompting speculation the retired general might be looking to revoke his admission of guilt.

Flynn pleaded guilty to lying to FBI agents www.reuters.com/article/us-usa-trump-russia/flynn-pleads-guilty-to-lying-on-russia-cooperates-with-u-s-probe-idUSKBN1DV50N about his 2016 conversations with Sergey Kislyak, then-Russian ambassador to the United States. Flynn was fired by Trump after just 24 days in the job for misleading Vice President Mike Pence about the extent of his conversations with Kislyak.

Flynn's supporters have also raised questions about why the judge presiding over his case recently backed off a prior order and said the government did not need to disclose the transcripts of phone calls in December 2016 between Flynn and Kislyak.

Powell, a conservative commentator who frequently appears on Fox News, authored the book "Licensed to Lie: Exposing Corruption in the Department of Justice," which relates to the department's conduct during the investigation of Enron Corp.