John F. Kelly, the onetime chief of staff to former President Donald J. Trump, confirmed on Monday some of Mr. Trump’s most startling comments about service members and veterans, reeling them off in a statement in which he said his onetime boss had “contempt for our democratic institutions, our Constitution and the rule of law.”

“A person that thinks those who defend their country in uniform, or are shot down or seriously wounded in combat, or spend years being tortured as P.O.W.s are all ‘suckers’ because ‘there is nothing in it for them,’” he told CNN.

He went on: “A person that did not want to be seen in the presence of military amputees because ‘it doesn’t look good for me.’ A person who demonstrated open contempt for a Gold Star family — for all Gold Star Families — on TV during the 2016 campaign, and rants that our most precious heroes who gave their lives in America’s defense are ‘losers’ and wouldn’t visit their graves in France.”

The mention of “a Gold Star family” was a reference to Mr. Trump’s 2016 attacks on the parents of an Army captain killed in Iraq, which he made after they criticized him. Four years later, he suggested that Gold Star families might be to blame for infecting him with the coronavirus.

Mr. Kelly’s statement confirmed reporting from The Atlantic in 2020, which he declined to confirm at the time despite pressure from friends and associates to do so.

The attitude he described also matched an account last month from Gen. Mark A. Milley, the former chairman of the Joint Chiefs of Staff, who said Mr. Trump had chastised him for choosing an Army captain who lost a leg in Afghanistan to sing “God Bless America” at a ceremony because “no one wants to see that, the wounded.”

In his final speech as chairman last week, General Milley said — without naming Mr. Trump — that American troops took an oath to the Constitution, not “to a wannabe dictator.”

Mr. Kelly has been sharply critical of Mr. Trump in interviews in recent months, and contemporary reports from his tenure revealed tension between the two men.

A Trump campaign spokesman, Steven Cheung, said in a statement provided to NBC News that Mr. Kelly “has totally clowned himself with these debunked stories he’s made up because he didn’t serve his president well while working as chief of staff.”