Donald Trump's onetime Defense secretary said Sunday that the former president should not be trusted with the nation's secrets again should the allegations made in his federal indictment over his handling of classified documents prove true.

"Based on his actions -- again, if proven true -- under the indictment by the special counsel, no," Mark Esper told CNN's Jake Tapper on "State of the Union."

"It's just irresponsible action that places our service members at risk, places our nation security risk. You cannot have these documents floating around. They need to be secured," he said.

Trump has pleaded not guilty to 37 federal charges, including 31 counts of "willful retention of national defense information." The former president denies any wrongdoing.

Esper's critical remarks about his onetime boss follow damning language by another high-profile Trump administration official -- former Attorney General Bill Barr -- who said last week that Trump was "toast" if even half of the details in his indictment were true.

"The revelations are very troubling, disturbing," Esper said Sunday when asked by Tapper if Trump's actions put America's national security at risk. "Yes, I do. If the allegations are true that it contained information about our nation's security, about our vulnerabilities, about other items, it could be quite harmful to the nation. And, look, no one is above the law. And so I think this process needs to play out and people held to account, the president held to account."

Trump fired Esper as his Defense secretary in November 2020, shortly after Joe Biden was projected as the winner of the presidential election.