Bill de Blasio, the former mayor of New York City, was slapped with a nearly $500,000 fine by the Conflicts of Interest Board (COIB) for improper use of taxpayer dollars during his 2020 Democratic presidential nomination run.

De Blasio was ordered to repay the city $474,794, including a $155,000 fine – the largest ever issued by COIB – to compensate for his unethical use of NYPD officers on the campaign trail.

“Although there is a City purpose in the City paying for an NYPD security detail for the City’s Mayor, including the security detail’s salary and overtime, there is no City purpose in paying for the extra expenses incurred by that NYPD security detail to travel at a distance from the City to accompany the Mayor or his family on trips for his campaign for President of the United States,” the COIB board — a five-member committee appointed by the mayor, comptroller, and a public advocate — wrote in an order published on Thursday.

“The Board advised [the] Respondent to this effect prior to his campaign; Respondent [de Blasio] disregarded the Board’s advice.”

The former mayor’s legal team has filed a lawsuit challenging the ruling by arguing that it sets a dangerous precedent. “With today’s decision, the COIB has broken with decades of NYPD policy and precedent, ignored the professional expertise of the greatest law enforcement agency in the world, and violated the Constitution to boot,” Andrew Celli Jr., a lawyer representing de Blasio, argued in a statement.

“In the wake of the January 6th insurrection, the shootings of Congress members [Gabby] Giffords and [Steve] Scalise, and almost daily threats directed at local leaders around the country, the COIB’s action — which seeks to saddle elected officials with security costs that the City has properly borne for decades — is dangerous, beyond the scope of their powers, and illegal.”

De Blasio ultimately withdrew from the presidential race in September 2019, struggling to break the 1 percent support threshold among Democratic primary voters.

The fine adds to de Blasio’s growing financial and legal woes. In April, the Federal Election Commission, the body charged with overseeing campaign finance laws, imposed a $53,000 fine on the former mayor for improperly accepting contributions from two PACs set up by himself and his associates.

The former mayor also reportedly owes hundreds of thousands of dollars in lawyer bills to a prestigious law firm representing him in another campaign finance-related case.

After his failed presidential run, de Blasio also tried his hand at an open House seat in New York which he ultimately lost. Since leaving politics, the former mayor became a visiting fellow at Harvard University and an occasional lecturer at New York University.