MY rear was letting me down.

Swimsuit season approaches, but my butt wasn’t as buff as it could be.

The solution: a butt facial – microdermabrasion of the derriere, combined with a massage with a tightening gel and a masque that heats up and forms a cast of your caboose.

Just don’t try Googling it – you’ll get some nasty results. In fact, there’s only place that’s doing it professionally, at least, and it’s in Brooklyn.

Kristine Panariello, the owner of Spa Secret in Bay Ridge, claims to do about 20 of what she calls butt facials and butt lifts a week (at $250 a pop).

And her clients are not just strippers or nude models, but also “doctors, lawyers and other professional people who want to look great when they go to the beach.”

And yes, she says, her customers even include men – particularly those prone to what aestheticians like to call “buttke”: acne of the butt.

“Usually, their wives or girlfriends bring them in,” she said.

The other day, after slipping into something less comfortable – a disposable paper thong – I lay stomach-down, awaiting her ministrations.

First came a gentle cleansing and rubdown. Then, above the New Age music and the gurgling of a tranquility fountain, came an ominous whirring from the pink machine at my right.

“It’s a little aggressive,” Panariello said of the microdermabrasion machine, brushing its crystal tip against my forearm for a preview.

No kidding. It felt like my cheeks were being clawed by a cat – a very nasty, sharp-clawed cat.

Eventually, the pressure subsided into a gentle sandpapering as Panariello worked around my scar, the result of a recent snorkeling misadventure.

Then, after rubbing down the area with a mixture of collagen, ginseng and vitamin C, Panariello lay a piece of gauze over my backside and mixed the masque.

Composed of calcium sulfate and various orangey-smelling extracts, it looked like cake frosting and went on the same way – with a spatula.

Feeling foolish – and looking like a pair of giant cupcakes – I lay there as the stuff heated and hardened.

At last she pried it off, one cheek at a time, and showed me the results.

Bottom line: After the nearly hour-long procedure, my rear seemed a bit firmer and somewhat uplifted.

The tough part was sitting through the 45-minute subway ride back to Midtown – with a butt that tingled as if it had been freshly sunburned (or scratched by cats).

I kept standing up, pretending to look at the subway map – hoping the tingling would go away.

At home, I unveiled the results to my husband, who’d been forced to commit to memory the unbuffed version, since he refused to photograph it.

The verdict?

“Fractionally higher, and very smooth,” he said. “And I can barely see your scar.”

Get me to the beach.