Mayor de Blasio finally stopped patting himself on the back for a stellar storm cleanup on Wednesday — and admitted that the city did a lousy job plowing the Upper East Side.

De Blasio first claimed at a morning press briefing that sanitation crews did “a helluva job” removing snow across the city, but he did an about-face in the evening after talking to angry residents, who echoed a Post report about the plower outage.

“While the overall storm response across the city was well-executed, after inspecting the area and listening to concerns from residents earlier today, I determined more could have been done to serve the Upper East Side,” de Blasio said in a statement. “I have instructed the commissioner of the Department of Sanitation to double-down on cleanup efforts on the Upper East Side, and as a result, 30 vehicles and nearly 40 sanitation workers have been deployed to the area to finish the cleanup.”

Sanitation Commissioner John Doherty’s spokesman referred questions to de Blasio’s statement. Doherty said at an earlier press conference, “It is what it is. They can believe what they want. I know what some of our problems were.”

Isaac Martinez, 31, who works at a pizzeria on Lexington Avenue, called de Blasio’s comments “too little, too late.”

“We needed those plows yesterday, because the snow really hurt business,” he said. “Next time, he’ll know better.”

The city’s treatment of the Upper East Side is the reverse of the outer-borough neglect then-Public Advocate de Blasio claimed in a letter to then-Mayor Mike Bloomberg about the 2010 Christmas blizzard.

De Blasio wrote it was “evident that the outer boroughs have been disproportionately affected by the lack of plowing.”

On Wednesday, many streets in Brooklyn were cleared down to the pavement, while major Manhattan roads remained slick and slushy. Pedestrians tumbled to the ground near the UN in front of Dag Hammarskjold Plaza.

Pedro Aponte, 48, was sweeping and salting a sidewalk nearby when he saw a man crack his head in the middle of the street.

“He slipped once, but he didn’t fall. He held his balance. Then he kept walking, and lost his balance again and he couldn’t stay up that time,” Aponte said. “His head bounced and hit twice.”

At the corner of West 55th Street and Seventh Avenue, a tractor-trailer got stuck at midday, its wheels spinning as the driver tried to get some traction.

The big rig blocked all traffic on West 55th Street and a lane on Seventh Avenue for about 10 minutes before the driver finally rocked it free.

At the corner of Seventh Avenue and West 43rd Street, a helpless cabby needed passers-by to push his taxi free after it got stuck in the snow.

“This is madness. This is bad, bad. Why is it not cleared?” he muttered.

In Times Square, software engineer Richard Yu, 27 — walking with a cane to a physical -therapy appointment — was bewildered as he tried to figure out how to navigate Broadway and West 42nd Street.

“The streets should be clean already,” fumed Yu, who lives in the Financial District.

On the Upper East Side, two apartment-building maintenance workers sick of seeing pedestrians fall took matters into their own hands and shoveled out the crosswalks at Third Avenue and East 78th Street.

Some locals were furious with the mayor and said his mea culpa isn’t enough.

“He screwed up, plain and simple. He can’t just take care of the people who voted for him,” said Erdem Durmaz, 37.

“De Blasio is new and needs to learn from this, or he’ll spend the next couple years writing apology letters.”

Additional reporting by Antonio Antenucci, Kirstan Conley, Beth DeFalco, Frank Rosario and Amber Sutherland