Mayor Bill de Blasio on Friday said he referred an alleged “criminal act” by the Trump Organization to the Manhattan District Attorney after reading a report that claimed the president’s family business underreported the value of properties, cheating the city out of taxes.

“One of the specific issues…was referred to the DA because there is a possibility of a criminal act having been committed,” Hizzoner said on his weekly WNYC radio appearance.

“At least one piece of what was found was serious enough to be referred to the DA,” he said, referencing an October story published by the nonprofit news outlet, ProPublica.

He did not provide additional details but a spokeswoman later said that the referral was made in November.

“ProPublica and WNYC’s investigation raised questions about what was reported to the Tax Commission versus bank lenders. The Manhattan DA is the proper jurisdiction to investigate these claims, as the city can only review what is directly reported to us. The DA has the jurisdiction to take appropriate steps if they find wrongdoing,” the spokeswoman said.

The report alleged that the Trump Organization gave starkly different figures for two of its Manhattan buildings — 40 Wall St. and the Trump International Hotel and Tower — to city tax authorities as opposed to what it told lenders. An expert called the discrepancies a “version of fraud.”

A source close to the Trump Organization dismissed de Blasio’s referral.

“What he’s saying is complete nonsense and it’s just another effort to distract from the multiple of investigations into his campaign and administration,” the source said, referring to a Federal Election Commission probe into fundraising irregularities from de Blasio’s failed 2020 bid and a city Department of Investigation look at the mayor’s use of his NYPD security detail during the presidential campaign.

A rep for Manhattan District Attorney Cyrus Vance Jr. declined to comment saying the office does not confirm investigations.