Former top cop Ray Kelly ripped Mayor de Blasio on Wednesday, saying Hizzoner has thrown the NYPD under the bus — and questioned the way Hizzoner claims that the city is safer than ever.

“My problem with Mayor de Blasio is when he got elected mayor, he didn’t go forward with an appeal on the stop-and-frisk case,” Kelly told MSNBC’s “Morning Joe” program,

“It besmirched the entire reputation of the New York City Police Department.”

Kelly said that de Blasio’s repeated claim that the city just saw its safest summer in 20 years conveniently ignored the fact that murders are up about 8 percent since the start of the year.

“We’ve never measured it like that before,” Kelly said of the seasonal statistic.

“We usually measure by the year. This is a new approach to doing business, and we’ll see if it works for Mayor de Blasio.”

Kelly was promoting his memoir, “Vigilance: My Life in Public Service and Protecting New York City.”

In the interview, he blamed de Blasio’s attitude toward the NYPD for encouraging cops to remain in their patrol cars rather than actively fight crime.

“I think it’s only common sense. They’re more reluctant to get out. There’s all sorts of signals that have been given to them that [say] don’t engage, or engage certainly in a lesser level than you have in the past,” he said.

Kelly also said “the so-called Ferguson Effect” — along with the increased use of cameras — was inhibiting “proactive policing” and contributing to a murder spike nationwide.

“Obviously, it means that police officers are thinking twice before they engage,” he said.

Asked if he feared a return to the city’s “bad old days,” Kelly said, “Everybody has to be concerned about that possibility.”

“I think [Police Commissioner] Bill Bratton is a top-flight professional but the mayor sets the tone . . . That’s the key here.”

Kelly was noncommittal when asked if he harbored any desire to run for mayor.

“I’m honored when people say, that but I’m happy with what I’m doing right now, thanks,” he said.