A nonpartisan ethics watchdog on Monday hailed the Federal Election Commission’s earlier decision to impose a $53,100 fine on committees tied to former New York City Mayor Bill de Blasio’s failed 2020 presidential campaign.

The FEC’s report detailing the de Blasio fine, which was handed down last month, was among a handful of closed cases that were officially made public late last week.

The commission issued the fine after the Foundation for Accountability and Civic Trust (FACT) and nonprofit Campaign Legal Center filed a complaint in 2019 alleging de Blasio’s campaign had allowed donors to improperly donate to the ex-mayor’s presidential bid by routing money through two political action committees.

“There is no gray area here. You simply can not use a state PAC as a slush fund for a presidential campaign,” FACT executive director Kendra Arnold said in a statement Monday.

In its report, the FEC said the de Blasio campaign admitted it accepted $52,851.89 from the NY Fairness PAC for travel and digital services and $123,000 from the Fairness PAC for polling.

The PACs were set up by de Blasio and others and the donations weren’t disclosed in campaign filings, the FEC said.

Under federal law, de Blasio’s campaign was prohibited from accepting contributions in excess of $2,800 from his state PAC and $5,000 from his federal PAC.

“The most his state PAC could have contributed is $2,800, yet de Blasio accepted an in-kind contribution of over $52,000 and used an additional $123,000 from his federal PAC for his campaign,” Arnold said.

“In the end, justice prevailed and the FEC held de Blasio and his federal campaign accountable by enforcing a civil penalty in this case. FACT is pleased to have achieved this result.”

The de Blasio campaign agreed to pay the fine and amend its FEC filings, according to the commission’s report.

“There were some accounting errors here and we immediately worked to get it right. We are happy to have it settled,” de Blasio adviser, Peter Ragone, said in a statement last month when the FEC’s decision was handed down.

With Post wires