Hillary Clinton's chief of staff privately told colleagues that President Barack Obama had falsely claimed he was unaware of Clinton's use of a private email system while she was secretary of state, hacked emails reveal.

"We need to clean this up," top Clinton aide Cheryl Mills told campaign chairman John Podesta in an email a month before Clinton's campaign officially launched. She was responding to Obama's claim that he found out about Clinton's personal email address at "the same time everybody else learned it through news reports."

"He has emails from her – they do not say state.gov," Mills told Podesta.

The email came less than a week after the New York Times broke the story on Clinton's use of a private email address to conduct official State Department business.

Subsequent interviews by the FBI in the course of its probe into Clinton's email practices revealed that Obama had emailed Clinton at her personal address using a pseudonym.

Two days after Mills' email, White House press secretary Josh Earnest acknowledged that Obama had emailed Clinton at her personal address, but said that was consistent with his public remarks.

"The point that the president was making is not that he didn’t know Secretary Clinton’s email address, he did," Earnest said. "But he was not aware of the details of how that email address and that server had been set up or how Secretary Clinton and her team were planning to comply with the Federal Records Act."

However, the wording of the question to Obama appears to contradict that explanation.

Though personal email accounts can be hosted by virtually every major email provider—services such as Gmail and Yahoo—Obama was asked specifically about Clinton's use of an email system "outside the U.S. government," which would include not just a private email server but an account hosted by anyone other than the State Department.

Mills' email was one of thousands released by the group Wikileaks after hackers believed to be acting in concert with the Russian government breached Podesta's personal email account.

Additional hacked emails show Clinton confidantes worried about the fallout from the Times story, including one who suggested that Clinton and other aides using her private email system knew what they were doing could land them in hot water.

"Why didn't they get this stuff out like 18 months ago? So crazy," wrote Center for American Progress president and informal Clinton adviser Neera Tanden in an email to Podesta on the day the Times story broke.

"I guess I know the answer," she wrote in a follow-up. "They wanted to get away with it."

Podesta appeared to acknowledge that Mills and Clinton aides David Kendall and Phillip Reines had been misleading about their roles in about the email controversy.

"Speaking of transparency, our friends Kendall, Cheryl and Phillipe sure weren't forthcoming on the facts here," he wrote to Tanden.

Reines was later denied an official role on the Clinton campaign after a long email diatribe in response to Washington Free Beacon inquiries into his and Clinton's email practices.