(CNN)The use of personal email to conduct government business has yet another Obama administration official under scrutiny.
Ashton Carter used personal email for some government business
The New York Times reported Thursday that Secretary of Defense Ashton Carter did so for part of his official work in the first months after taking on his duties, referring to emails it had obtained copies of.
The Defense Secretary reportedly kept using private email after news about Hillary Clinton's use of a personal email server during her service as secretary of state triggered attacks by Republican lawmakers.
Carter told reporters traveling with him in the Middle East Thursday that he had made a mistake and ended the practice a few months ago.
"Someone in my position should have known better. I did not do the right thing," he said.
Both Carter and Clinton have said they have not put sensitive information in jeopardy.
Sen. John McCain, chair of the Armed Services Committee, called Carter's use of personal email "hard to believe" in light of the intense focus of public attention aimed at Clinton's use of personal email.
"With all the public attention surrounding the improper use of personal email by other administration officials, it is hard to believe that Secretary Carter would exercise the same error in judgment," McCain said in a statement Thursday morning.
McCain said his committee requested copies of Carter's emails "and will be conducting a review to ensure that sensitive information was not compromised."
Carter reportedly conducted a portion of his work via personal email, whereas the former secretary of state used a private server primarily to conduct business via email.
No evidence of wrongdoing has come to light in her case, and her private server did not break State Department rules.
Some critics have charged that Clinton's use of a private email server skirted the preservation of her communications on government servers as a long-term record. Clinton has turned over some 55,000 pages of emails to the State Department.
But FBI investigators have been examining her emails for months, which has made headlines and drawn continued criticism. They have reviewed them to see if classified materials have been mishandled but have so far not said this is the case.
Carter's use of private email could now draw similar fire.
The Pentagon issued a statement saying Carter has done nothing wrong. It said that the defense secretary uses email sparingly, preferring phone or personal conversations.
"He does have a personal email account that he uses to correspond primarily with friends and family. Any email related to work received on this personal account, such as an invitation to speak at an event or an administrative issue, is copied or forwarded to his official account so it can be preserved as a federal record as appropriate," said Peter Cook, Pentagon press secretary.
"Secretary Carter does not use his personal email or official email for classified material," Cook said. His team provides him with secure classified information, at times as hard copies.
He also said that Carter has "stopped such use of his personal email and further limited his use of email altogether."