“A complete lack of accountability” under Mayor Bill de Blasio is to blame for a deed lifting to allow a nonprofit nursing home on Manhattan’s Lower East Side to be flipped to luxury condos and a $72 million profit, according to an investigation released Thursday by the city’s corruption watchdog.

In a 161-page report, the Department of Investigation found that City Hall “knew or should have known” about the land deal at the site known as Rivington House, which had served AIDS patients.

The report questions the mayor’s long-standing insistence that City Hall was snookered by greedy developers and de Blasio had no clue they intended to convert the property to luxury condominiums.

“DOI’s investigation further revealed a complete lack of accountability within City government,” the report said. It also found that “several City employees knew the property owner considered selling the property for conversion to luxury housing” and that the developer could legally do so without the restrictive covenant.

VillageCare, the owner of the site at 45 Rivington St., bought the property in 1992, with the deed restrictions limiting it to a nonprofit medical facility. The owner sold the property to the Allure Group in 2015 for $28 million, paid the city $16.15 million to lift the deed restrictions, and Allure sold the property this year for $116 million to luxury-condo developers.

The push to lift deeds was led by one of the mayor’s top fundraisers, James Capolino. He was an early supporter of de Blasio’s bid to the mayoralty and became the city’s top-earning lobbyist after the mayor took office, according to a published report. He could not be immediately be reached for comment.

The controversy over Rivington is one of at least five fundraising investigations of de Blasio and his inner circle by city, state and federal agencies.

In a statement, mayoral spokesman Eric Phillips said, “This review found no evidence that the mayor knew of any part of this transaction and no evidence that any government official was involved with any illegal or unethical behavior.”

The DOI report concluded that officials at the highest levels of government — including First Deputy Mayor Tony Shorris and Stacey Cumberbatch, then-head head of the city’s administrative-services agency — knew what has going on.

“Congratulations! Thank you and staff for great work and bringing this to closure in the best interest of the city,” a Nov. 10, 2015, email from Cumberbatch said, the report quoted. “Much appreciated.”

Cumberbatch was quietly transferred to the city’s public hospitals corporation earlier this year.

The report hints at probers’ frustration with the de Blasio administration, which was “hindered by” de Blasio’s lawyers’ “lack of cooperation.”

Despite an executive order mandating that investigators get unfettered access to documents and city computers, de Blasio’s law department once handed over 1,000 pages of relevant documents — 990 of which were blank.