Recidivist criminals committed or were killed in nearly one of every five New York City murders last year — leading Mayor Bill de Blasio to express “real concerns about the parole system” on Thursday.

NYPD statistics show that parolees and probationers were involved in 19 percent of the 289 murders recorded during 2018, marking the second year in a row that percentage increased, officials revealed during a news conference at the 67th Precinct station house in Brooklyn.

“We have real concerns about the parole system,” de Blasio said.

“And while we can say there’s things where we want to see reform [in the criminal justice system], we can also say there’s things where we want to see some tightening up.”

The mayor said his administration planned to lobby Albany lawmakers for changes in state law “to give judges the right to consider the dangerousness of an individual brought before them in determining whether to grant bail or not.”

“We obviously are going to be talking to our own probation department to make improvements as well,” he added.

Currently, New York judges can only set bail based on the likelihood that a defendant will return to court to face charges.

By contrast, federal judges are allowed to consider criteria that include “danger to the community or any other person.”

De Blasio previously called for tougher bail laws in 2015, following the murder of NYPD cop Randolph Holder by a drug dealer who was free on bail.

But since then, he has largely championed the progressive policy of eliminating bail for low-level, non-violent offenders.

The mayor said he would continue that effort, but noted that a crackdown on bail for ex-cons “has to be addressed in Albany as well.”