The head of the Environmental Protection Agency (EPA) once called President Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE an "empty vessel" when it comes to his knowledge of the Constitution, CNN reported on Monday.

Scott Pruitt Edward (Scott) Scott PruittJuan Williams: Swamp creature at the White House Science protections must be enforceable Conspicuous by their absence from the Republican Convention MORE criticized then-candidate Trump's ability to uphold the Constitution as president in an interview with an Oklahoma radio show in February 2016.

"I think he's an empty vessel when it comes to things like the Constitution and rule of law," Pruitt said on the "Exploring Energy" radio show. "I'm very concerned that perhaps if he's in the White House, that there may be a very blunt instrument as the voice of the Constitution."

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Pruitt at the time of his comments was backing Jeb Bush's Republican presidential campaign.

Pruitt, who served as attorney general in his home state of Oklahoma, also compared Trump to former President Barack Obama Barack Hussein ObamaThe Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon Trump appointees stymie recommendations to boost minority voting: report Obama's first presidential memoir, 'A Promised Land,' set for November release MORE, saying in the interview that Obama at least had the wherewithal to know how to hide his "unlawfulness."

"This president, the one we have there now, has at least tried to nuance his unlawfulness," Pruitt said. "He at least sits back and says, 'How do we break the law and so where it's really tough to show that we have?' I'm not sure that Donald Trump would."

The newly unearthed interview is the second to come to light in the past week in which Pruitt criticizes Trump.

During a Senate Environment and Public Works Committee hearing on Capitol Hill last Tuesday, Pruitt was asked by Sen. Sheldon Whitehouse Sheldon WhitehouseLWCF modernization: Restoring the promise Restaurant owner defends calamari as 'bipartisan' after Democratic convention appearance Warren calls on McConnell to bring Senate back to address Postal Service MORE (D-R.I.) about comments he made at another local Oklahoma radio station in February 2016.

In that audio, Pruitt said Trump as president would be "more abusive to the Constitution than Barack Obama."

Pruitt responded to both audio releases with the same statement, saying, “After meeting him, and now having the honor of working for him, it is abundantly clear that President Trump is the most consequential leader of our time. No one has done more to advance the rule of law than President Trump. The President has liberated our country from the political class and given America back to the people."