The father of the American student left comatose after 18 months in a North Korean prison has criticized former President Barack Obama for not doing enough to free his son.

“The question is, ‘Do I think the past administration could have done more?’ ” Fred Warmbier, Otto Warmbier’s dad, said at a press conference in Ohio on Thursday. “I think the results speak for themselves.”

He said he appealed to government officials, from members of Congress to former Secretary of State John Kerry, to help free his 22-year-old son, who was jailed for removing a propaganda poster in 2016.

Fred said he was told to stay quiet so as not to “upset” the North Koreans.

“We relied on this false premise that they would treat Otto fairly and let him go,” he said.

He noted that President Trump called him this week and said, “I’m sorry about the outcome.”

The elder Warmbier’s criticism came as doctors at the hospital in Cincinnati where the young man is being treated revealed he is suffering from severe brain injuries.

The doctors said Otto Warmbier shows extensive loss of brain tissue consistent with respiratory arrest, when oxygen to the brain is cut off, but they aren’t sure why.

He shows no sign of understanding language or awareness of his environment.

The University of Virginia student returned to Ohio on Tuesday.

North Korea claimed the young man slipped into a coma after suffering from botulism and taking a sleeping pill.

Fred said he does not believe that at all, and a report in the New York Times said US intelligence officials say Otto was severely beaten.

With wire services