Screen Shot 2015 09 01 at 7.22.21 AMFox News/screengrabFormer Vice President Dick Cheney.

Former Vice President Dick Cheney said Monday that former Secretary of State Hillary Clinton should be extremely concerned about the email controversy dogging her campaign.

“I think it’s very, very serious. I don’t think it’s something you’re going to be able to just blow away,” Cheney said on Fox News.

Cheney said he was particularly concerned that Clinton, now the Democratic presidential front-runner in 2016, left classified information vulnerable by exclusively using a personal email system for her government work.

“I think it’s significant,” Cheney said. “I know from my own experience that when you go into those kinds of jobs, you’re briefed on the enormous importance of being very careful with how you handle classified information. In fact, it looks to me like she approached it in a sort of amateurish, nonprofessional way.”

Clinton and her team have struggled to contain the negative implications of the email story, which kicked off in March after The New York Times revealed that she only used a private, non-government email while at the State Department. 

Clinton and the State Department insist that none of the emails were classified at the time, and Clinton’s allies often point to past secretaries of state using private email accounts. However, an increasing number of her communications are being retroactively marked classified as the State Department slowly releases them in batches, including late Monday night.

Cheney’s criticism of Clinton comes as he promotes his new book, “Exceptional: Why the World Needs a Powerful America,” which he wrote with his daughter, Liz Cheney.

U.S. Democratic presidential candidate Hillary Clinton listens to a question from the audience during a community forum about substance abuse in Keene, New Hampshire August 11, 2015. REUTERS/Brian Snyder/Thomson ReutersHillary Clinton.

In another interview, on CNN, Cheney said that US foreign policy adversaries like China and Russia probably have access to Clinton’s emails and any secret information within them. 

“They’ve got my personnel records. How can they not have her emails?” Cheney asked, an apparent reference to the massive Office of Personnel Management data breach linked to the Chinese government.

Cheney, a fierce Republican critic of how Democrats handle national security issues, went on to say Clinton “should have known better.” 

“I think it was sloppy and unprofessional — that it reflected a lack of understanding for how easy it is for adversaries to tap into communications,” he said on CNN. “Maybe she went into it ignorant but I find that hard to believe. She’s an intelligent woman, She’s spent a lot of time in the White House.”

View Cheney’s Fox News interview below: