WASHINGTON (CBSDC/AP) — Former White House Press Secretary Robert Gibbs believes it’s “highly unusual” that former Secretary of State Hillary Clinton would use a personal email account, and not a governmental one, during her time at the State Department.

The New York Times reports that Clinton only used a personal account to conduct government business over email as secretary of state. By doing so, it “may have violated federal requirements that officials’ correspondence be retained as part of the agency’s record,” according to The Times.

The former press secretary for President Barack Obama told NBC’s “Today” he can’t think of a reason why Clinton wouldn’t have a government email account.

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“I think it is obviously highly unusual. There are lots of briefings that you have when you go into the White House about preserving any email that you have, making sure that it’s part of your official account,” he said.

Gibbs said that Clinton’s camp needs to get out in front of the email story.

“I think it’s something that they’re going to have to explain in good measure today and probably figure out how to get a lot of those emails, or as many as they can, back in the archives,” Gibbs told “Today.”

Gibbs added that this will be perfect fodder for critics to hit back at the former secretary of state.

“I think there’s no doubt. I think it’s another one of those things the Clinton campaign – such as it is – is going to have to explain,” Gibbs said. “I think it’s much easier for critics to explain why they don’t exist than it might be for her to explain why she used her private email.”

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Clinton’s office said nothing was illegal or improper about her use of the non-government account and that she believed her business emails to State Department and other .gov accounts would be archived in accordance with government rules.

“Like Secretaries of State before her, she used her own email account when engaging with any department officials,” Clinton spokesman Nick Merrill said. “For government business, she emailed them on their department accounts, with every expectation they would be retained. When the department asked former secretaries last year for help ensuring their emails were in fact retained, we immediately said ‘yes’.”

“Both the letter and spirit of the rules permitted State Department officials to use non-government email, as long as appropriate records were preserved,” he said.

Potential Republican presidential candidate Jeb Bush has already gone on the offensive against Clinton. The former Florida governor tweeted that Clinton’s unclassified emails should be released.

“Transparency matters. Unclassified Hillary Clinton emails should be released. You can see mine, here. jebbushemails.com,” Bush posted on Twitter.

Deputy State Department spokesperson Marie Harf defended Clinton in a statement to CBS News.

“The State Department has long had access to a wide array of Secretary Clinton’s records – including emails between her and Departments officials with state.gov accounts,” Harf said.

The Wall Street Journal reports Clinton is expected to announce her presidential run next month.

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