They’re at it again. Hamptons socialite Whitney St. John is being accused by her ex, James Fairchild, of surreptitiously squirreling away hundreds of thousands in jewelry rather than turning over the pricey baubles to a ­court-ordered estate sale in their bitter divorce battle.

St. John and Fairchild’s possessions were sold over the weekend in a high-end Estates NY tag sale at their Bridgehampton marital home, which raked in $350,000 on its first day, sources said. The Memorial Day weekend sale included more than 200 paintings plus cars, minks and furniture, and was ordered after the couple couldn’t agree on dividing up their possessions.

But St. John, who objected to the court-ordered sale, is being accused of holding back baubles valued at up to $300,000 retail, and Fairchild could seek to hold her in contempt.

“Whitney refused to hand over the jewelry for the sale,” a source sniffed, adding the sale would’ve reached $750,000 if it had included the jewelry.

The couple’s been in an ongoing battle over a small fortune in jewelry they’d bought together to launch a high-end Hamptons store before their 2011 divorce case.

But St. John’s lawyer huffed: “We contend that Mr. Fairchild has done exactly what he claims Whitney did, intercepting valuable store inventory and not producing it per court order for the auction.”

He added that he wants Fairchild held in contempt for selling off a 1955 Jaguar for $175,000 and not splitting the proceeds with St. John. But a source close to Fairchild denied that claim, saying, “The car was a gift to James. He sold it for $105,000. He plans to give half the proceeds to Whitney, which the court is aware of.”

Fairchild got to pocket $15,000 at the sale, sources said, upon realizing that one painting had been in his possession since before he married St. John in 1994.

Court documents reveal the couple is due back in court June 16 over the jewelry issue.