“Broken Windows” is getting smashed to pieces.

Starting next month, the city is tossing 700,000 old warrants seeking arrest for low-level crimes such as public urination, sources said — reversing decades of strict enforcement.

Mayor de Blasio, the NYPD and four of the city’s five district attorneys have signed off on the plan, which would apply only to warrants older than 10 years, according to a spokeswoman for

City Council Speaker Melissa Mark-Viv­erito, who has pushed for the amnesty.

But de Blasio’s Republican election challenger, Nicole Malliotakis, argued that the scheme would encourage more scofflaws.

“What is the deterrent then for individuals to not commit quality-of-life crimes?” she fumed. “There’s no criminal penalty and now there’s gonna be a civil penalty that’s not enforced.”

The soon-to-be-tossed warrants were issued over the years mostly against people who failed to appear in court after being slapped with summonses for infractions such as public urination, littering and various subway offenses, ­according to police.

Citywide, there are more than

1.5 million such outstanding warrants, Manhattan DA Cy Vance Jr. testified before the council in March, adding that there are some 200,000 in Manhattan alone.

The warrants will likely be dismissed by “August or September,” according to Larry Byrne, the NYPD’s deputy commissioner for legal matters, who said there will be “some exceptions.”

The city will not forgive quality-of-life warrants if an individual also has an active felony warrant, he said.

Mark-Viverito called the amnesty push a “tremendous and necessary undertaking,” according to NY1.

Richmond County District Attorney Michael McMahon — the only DA not to endorse the plan — ­declined to comment.

The amnesty program is the latest instance of the de Blasio administration moving away from the NYPD’s “Broken Windows” method of policing, which assumes that aggressive efforts to halt minor infractions also leads to a drop in major crimes.

Last summer, the mayor signed the council’s controversial Criminal Justice Reform Act, which decriminalizes quality-of-life infractions — making them civil rather than criminal offenses.

The new rules allow cops to issue summonses for quality-of-life infractions — although officers retain the prerogative to make arrests in such cases.

Additional reporting by Max Jaeger