Talk about giving away the store: Mayor Bill de Blasio said last week that he is still pushing his deranged campaign to make Albany impose a “retail-vacancy” tax on landlords unfortunate enough to have empty stores in their buildings.

Sure, let’s squeeze owners who are stuck with acres of space left behind by Dean & DeLuca, the once-great food chain that was ruined not by high rent, but by Bangkok-based owners who ran it into the ground. Or landlords facing the coming bloodbath at Forever 21, which plans to file for bankruptcy and close 178 US stores.

As scary as de Blasio’s tax push is, still worse is his silence on an insidious bill snaking its way through the looney-left City Council. A normal mayor would have put the kibosh on it from day one. The so-called “Small Business Jobs Survival Act” would impose a form of rent control on commercial landlords, interfere in lease negotiations and generate even more dark storefronts than there are already.

In fact, the explosion in new-storefront creation by new development over the past 15 years — not unaffordable rent hikes — is the biggest reason for a proliferation of “Prime Retail for Rent” signs. How could so much extra new space be filled at the same time the online share of shopping jumped from 0 to nearly 10%?

The socialist mind would sooner blame landlords. Hey, they even get tax breaks for keeping storefronts dark! Which in fact is a myth.

De Blasio’s socialistic “solution” to a perceived “retail crisis” raises the question: Is there a “crisis” at all? Because quantifying retail ­vacancy is much harder than for ­office space; it isn’t even clear how much empty store space there is in the five boroughs.

That’s because there are different ways to count. In his study on the “Trends and Causes” of retail vacancy, for example, city Comptroller Scott Stringer last week cited a 5.8% vacancy rate based on square footage. A survey by the Department of City Planning last summer claimed a 9% rate based on the number of empty storefronts. Many real estate brokers say it’s between 10% and 15%.

In any case, the “crisis” mainly ­affects certain stretches in high-visibility parts of Manhattan such as Bleecker Street and Broadway in the 50s. In some parts of town, such as in bustling Jackson Heights, barely 5% of storefronts are empty, reports the DCP.

Whatever the true number, if de Blasio knew anything about the city he only pretends to lead, he’d know they have only rarely to do with greedy property owners.

He surely won’t have time for the findings of Stringer and of the DCP, which both attributed retail ­vacancies to many different factors, rent being only one. After all, he didn’t look at Stringer’s ­audit on lead-poisoned kids at NYCHA projects, either.

The survey by his own DCP commissioner, Marisa Lago, noted, “The reasons for storefront vacancies are complex and varied,” including the impacts of internet shopping, maddeningly complex city regulations and “a significant amount of newly constructed storefront space,” which increases supply whether there is demand or not.

How significant? Stringer said the number of retail storefronts, occupied or not, in the city rose nearly 20% from 2007 to 2017.

Stringer cites the “Amazon effect” of online shopping and regulatory hurdles that make life miserable for owners of shops and restaurants (e.g., endless delays in getting city approval for building alterations and SLA approval for liquor ­licenses — both are “significant drivers of retail vacancy.”)

Yes, the report says, rising retail rents — up 22% from 2007 to 2017 — had an impact. But at least some of that was due to greed on the part of City Hall, not of landlords: To wit, skyrocketing property taxes, a portion of which tenants are usually obligated to pay.

Yet because Stringer’s numbers are two years old, they omit that ­retail rents plunged an average of 18% over the past year, according to both the Real Estate Board of New York lobbying and research organization and major commercial real estate brokerage CBRE.

The retail scene is troubled enough. De Blasio would bring it to utter ruin in service to his “progressive” agenda. Store owners might soon wish that he’d stayed in Iowa for good.

scuozzo@nypost.com