A former federal prosecutor is urging New York Attorney General Letitia James to investigate a foundation set up to protect the legacy of artist Helen Frankenthaler — but which is instead, allegedly, promoting the interests of its directors, The Post has learned.

Among the allegations is that board member Clifford Ross, who is a nephew of the late painter, persuaded the board to shell out hundreds of thousands in grants to the Asia Society and Museum, which is hosting a show of Ross’s own photos. A giant poster featuring Ross’s photos and his name is wrapped around the front of the Manhattan museum’s Park Avenue facade.

In a June 5 letter sent to James and James Sheehan, chief of the state’s Charities Bureau, attorney Andrew Weissman says he is writing to “bring your attention to serious allegations of systematic abuse and conflicts of interest” in the Helen Frankenthaler Foundation.

The organization was set up in 1984 to protect and promote the legacy of the abstract artist, who died in 2011.

“I request that you independently investigate what appear on their face to be blatant and repeated acts of self-dealing and undisclosed conflicts of interest by members of the board of directors of the Frankenthaler Foundation,” Weissmann writes in the letter, as seen by The Post.

Between 2021 and 2022, the Foundation, which has assets of more than $500 million, doled out $250,000 in grants to the Asia Foundation and Museum, according to IRS filings. Ross’s photographs of waves in Portugal, which now adorn the front of the museum, are part of “Coal + Ice.” The “immersive photography and video exhibition” opened in February and closes Aug. 11.

Last year, Frederick Iseman, an ousted board member of the Frankenthaler Foundation and another Frankenthaler nephew, sued the foundation in New York State Supreme Court. Among the other board members are Lise Motherwell, the late painter’s stepdaughter.

That lawsuit, which is ongoing, accuses the defendants of “engaging in a kind of ‘grabstract expressionism’ that is effectively destroying Frankenthaler’s legacy.”

Weissmann — a former prosecutor in Robert S. Mueller’s Special Counsel Office probe of alleged Russian interference in the 2016 election — writes that he contacted the AG at the behest of former longtime board member Iseman and his attorneys at Kaplan, Hecker and Fink LLP.

“Mr. Iseman has made clear that he is taking these steps solely out of his interest in the legacy of his aunt and the proper and lawful functioning of the Frankenthaler Foundation,” the letter says.

“While it is impossible to comment with specificity on a letter that we have not seen, it appears clear that Mr. Iseman, this time via surrogates, continues to engage in scorched earth tactics designed to harm the reputation of the Foundation’s directors … We have already responded fully to these baseless allegations in court filings,” a representative for the Frankenthaler Foundation said in a statement to The Post.