NEW YORK • U.S. Rep.-elect George Santos of New York was under investigation by Long Island prosecutors Wednesday, after revelations surfaced that the now-embattled Republican lied about his heritage, education and professional pedigree as he campaigned for office.

Despite intensifying doubt about his fitness to hold federal office, Santos has shown no signs of stepping aside — even as he publicly admitted to a long list of lies.

Nassau County District Attorney Anne Donnelly, a Republican, said the fabrications and inconsistencies were “nothing short of stunning.”

“The residents of Nassau County and other parts of the third district must have an honest and accountable representative in Congress,” she said. “If a crime was committed in this county, we will prosecute it.”

Santos’ campaign did not immediately respond to a request for comment Wednesday.

He is scheduled to be sworn in next Tuesday, when the U.S. House reconvenes.

If he assumes office, he could face investigations by the House Committee on Ethics and the Justice Department.

Santos suggested he does not plan to step aside in a Twitter post Wednesday about a visit to the U.S. Merchant Marine Academy earlier in the day.

“In Congress, I look forward to working alongside them to fully utilize this amazing resource we have in our own backyard in #NY03,” the tweet said.

The Republican has admitted to lying about having Jewish ancestry, a Wall Street pedigree and a college degree, but he has yet to address other lingering questions — including the source of what appears to be a quickly amassed fortune despite recent financial problems, including evictions and owing thousands in back rent.

Fellow Long Island Republican, Rep.-elect Nick Lalota, said he was troubled by the revelations.

“I believe a full investigation by the House Ethics Committee and, if necessary, law enforcement, is required,” Lalota said Tuesday.

The New York attorney general’s office has already said it’s looking into issues that have come to light.

A spokesperson for the Nassau County DA’s office, Brendan Brosh, said Wednesday: “We are looking into the matter.”

The scope of the investigation was not immediately clear.

Other Republicans castigated Santos but stopped short of asking him to step aside.

“Congressman-Elect George Santos has broken the public trust by making serious misstatements regarding his background, experience and education, among other issues,” said Joseph Cairo, chair of the Nassau County Republican Committee, which is within the 3rd Congressional District.