New York City Mayor Bill de Blasio treated his New York Police Department-provided security detail like a "concierge service" that drove around his son, staff members and guests even when he was not in the car and helped his daughter move out of her apartment, the city's Department of Investigation alleged in a report released Thursday.

       The investigative report by the city’s anti-corruption watchdog also accused the mayor of failing to reimburse the more than $300,000 his security detail spent on travel outside New York City during de Blasio's unsuccessful 2020 run for president.

       "Protecting the mayor and his family is a serious and significant job that should be guided by best practices, formalized procedures, and an understanding that security details are not personal assistants in a dignitary's daily life but provide essential protection," DOI Commissioner Margaret Garnett said.

       The NYPD inspector in charge of the Executive Protection Unit, Howard Redmond, "sought to obstruct" the investigation by refusing to turn over a City Hall-issued phone, trying to destroy his NYPD-issued phone and demonstrating a "lack of candor" during an interview, the report claims.

       Redmond was referred to the Manhattan District Attorney's office for possible prosecution. While de Blasio is not facing prosecution, he could face potential ethics violations.

       "We are reviewing the referral," a spokesperson for Manhattan DA Cy Vance said.

       Pacific Press/LightRocket via Getty Images, FILE

       Chiara and her father, Bill de Blasio listen as Al Sharpton speaks in New York City, Dec. 25, 2015.

       In her response, de Blasio's press secretary Danielle Filson called the report "unprofessional" and "inaccurate," claiming that it was based on "illegitimate assumptions and a naive view of the complex security challenges facing elected officials today."