A diamond-dealing alleged tax fraudster fleeced a fellow jeweler out of more than $2.5 million — then used the money to pay off debtors in a shady shell game, a new lawsuit alleges.

Boris Aronov claims that Moshe Lax — who once co-owned Madison Avenue Diamonds with Ivanka Trump under the name Ivanka Trump Fine Jewelry — lured Aronov into a bogus multimillion-dollar diamond deal with Tiffany & Co., the new Manhattan Supreme Court lawsuit alleges.

In March 2017, Lax asked Aronov to use his good standing in the Diamond District — since Lax’s reputation had tanked amid debt problems — to buy $3 million in diamonds to be sold to Tiffany’s and the pair would split the profits, the court papers say.

But Lax didn’t actually have a deal with Tiffany. He instead took the diamonds, scrubbed and replaced their certification numbers and sold them on the open market, the court documents allege.

Lax “had no valid purchase orders from Tiffany and he had no intention to sell the diamonds supplied by Boris to Tiffany. Moshe did not disclose these facts to Boris,” the lawsuit claims.

Then Lax used the profits from the diamond sales to pay back Baruch and Judah Rosenfeld instead because he owed them millions, according to the court papers.

By August 2017, Aronov still hadn’t been paid by Lax and ended up footing the cost of the diamonds himself, the court documents allege. Lax eventually returned 44 of the diamonds to Aronov, who to date is still owed over $2.5 million in the bad deal, the court papers claim.

Aronov named the Rosenfelds as defendants in the suit for allegedly helping Lax pull off the ruse so they could recoup what they were owed at Aronov’s expense.

“Baruch and Judah encouraged Moshe to make the Tiffany Misrepresentations so that they could together obtain the Boris Diamonds and sell them on the open market and secure the proceeds therefrom to satisfy debts that Moshe owed to the Rosenfelds,” the court documents charge.

Lax — whom the feds have sued for $60 million in unpaid tax liabilities on his late father’s estate — was not named as a defendant in the lawsuit as he already entered into a $3 million judgment with Aronov in court in September 2017.

Aronov’s lawyer, Casey Murphy, told The Post, “We believe a fraud was committed upon Mr. Aronov and Mr. Lax did not act alone. Our investigation is ongoing.”

Ivanka Trump was not named as a defendant in the case, nor was she accused of any wrongdoing.

The federal lawsuit against Lax — which accuses Lax, his sister and late father of making a series of sham transactions to evade tax liability —- is still pending in Brooklyn federal court.

Lax and Judah Rosenfeld declined to comment. Baruch Rosenfeld did not immediately return a request for comment.