The much younger Polish wife of Upper East Side investment banker Robert B. Albertson has been busted by cops for harassing his ex, top hedge fund exec Suzanne Murphy, sources say.

Karolina Albertson, 28, was arrested on March 6, according to a police report, for second-degree aggravated harassment, a misdemeanor.

Sources say, Karolina — who met Sandler O’Neill chief strategist Albertson, 67, in the Hamptons while he was married to Murphy, 46 — threatened Murphy as she and Albertson waged a contentious child-custody battle over their daughter.

On Feb. 15, “Suzanne’s phone rang from Robert’s number four times in 12 minutes,” a pal said. “It was Karolina saying, ‘If you don’t leave my husband alone, I’m going to have your face smashed in!’ ”

Murphy filed a police report and Karolina was hauled in. She’s due for a desk appearance Monday. But a friend of Karolina sniffed, “Suzanne’s the one who’s been actively harassing Karolina.”

Albertson and Murphy married in 2007.

“Suzanne tried in-vitro 25 times,” said a source. When their child needed medical care in 2012, Murphy temporarily moved to Tampa, Fla., and “lived in a neonatal intensive care unit for 10 weeks. She knew nothing about this other woman.”

Murphy did not comment. A rep for Albertson called Murphy’s “ugly allegations” a “clear attempt to distract from her own non-compliance with terms of the custodial agreement…She has been the subject of multiple legal complaints over the last 10 months that she has denied Mr. Albertson access to their daughter.”

Karolina’s attorney, Thomas A. Kenniff, commented: “Any claim that Karolina harassed Ms. Murphy is utterly baseless. The allegations are nothing more than sinister tales born out of Murphy’s seeming unwillingness to accept the fact her husband has found happiness with a lovely younger woman. The real tragedy here, aside from the fact Mrs. Albertson had to suffer the indignity of arrest and prosecution, is the impact this situation is likely to have on the couple’s young child. As is so often the case in these situations, suffer the children.”