It’s official: the crucial fourth quarter was a clunker for Walmart.

Confirming an exclusive Jan. 31 report in The Post — which quoted a source as saying Walmart was “heading into another negative ‘comp’ for the quarter” — the world’s largest retailer said yesterday its fourth-quarter comparable sales, or sales at stores open at least a year, tumbled 1.8 percent.

The drop was even steeper than the worst-case scenario painted by Walmart in November, when executives told analysts that comparable sales might decline as much as 1 percent or increase as much as 2 percent.

As reported by The Post, Walmart last month was holding off orders of fresh spring merchandise as it scrambled to lower its inventory after a disappointing December.

Yesterday, Walmart execs likewise confirmed a Post exclusive of Jan. 25, which reported that the giant discounter was pressing its suppliers for more low-price goods to better compete with fast-growing dollar-store chains.

For example, Walmart is looking to mimic dollar stores by selling smaller boxes of detergent that are more affordable for shoppers in a pinch, even though they might be pricier on a per-ounce basis than a larger box.

“That’s something we’re addressing right now,” CFO Charles Holley told reporters yesterday.

Shares of Walmart tumbled $1.71, or 3.1 percent — its worst one-day drop in nine months — to close at $53.67.

In the fourth quarter, Walmart’s profit from continuing operations rose 4.2 percent to $5 billion while revenue climbed 2.4 percent to $115.6 billion.

The big box behemoth’s recent flipflopping on strategy has “alienated their core customer, as well as the customer that had traded down into their stores,” said Charles Grom, an analyst who cut his rating on Walmart shares last week.

The worst part of it is that Walmart executives still haven’t worked out a game plan to solve that problem, he added.

“You identify the issues first and fix them second,” according to Grom. “I don’t think they’ve even identified them yet.”jcovert@nypost.com