Mayor Bill de Blasio used a “shell game” to get around strict donor limits to bankroll his quixotic White House bid, a campaign finance watchdog charged Wednesday.

The complaint from the Campaign Legal Center alleges that the mayor improperly used two political committees he controls to pick up the tab for polling, advertising, rent and travel for his 2020 bid.

The move, the group claims, effectively allowed donors to give three times.

“The de Blasio campaign appears to have concocted a shell game to arrange for a small number of wealthy donors to illegally support de Blasio’s presidential run above and beyond legal contribution limits,” said Brendan Fischer, a director with the group.

“Contribution limits are designed to prevent corruption. Presidential candidates cannot lay the groundwork for their campaign by taking contributions of nearly triple the federal limits.”

The complaint is the second in as many weeks claiming that de Blasio’s three-headed political fundraising operation violated federal election laws.

De Blasio spokeswoman Olivia Lapeyrolerie said the campaign is “reviewing the complaint.”

The filing with the Federal Election Commission charges that Hizzoner circumvented fundraising limits by using his federal and state political committees — Fairness PAC and NY Fairness PAC — to pay for campaign expenses before and after he officially declared his White House bid.

The maneuver, it says, violated the law in two ways.

First, it allowed de Blasio to solicit additional money from contributors that hit donation limits to his presidential campaign. Then the complaint charges that de Blasio’s presidential campaign wrongly reported the assistance it received to avoid limits on how much PACs can donate to campaigns.

All told, the CLC counted at least 25 individuals who donated the legal maximum of $2,800 to de Blasio’s Democratic primary campaign and then contributed another $5,000 to his state and federal PACs.

Nearly three-quarters of the contributors — 18 of the 25 — gave to the PACs between March and May, when de Blasio was “putatively testing the waters for a presidential bid.”

The complaint also tallies 78 expenditures worth $148,000 made by de Blasio’s nonpresidential political committees — including his White House campaign launch video — that bolstered his bid, without simultaneously disclosing the donors.

The FEC complaints filed in August are the latest in a string of campaign finance scandals that have dogged de Blasio over the course of his political career.

Local and federal prosecutors nearly indicted de Blasio in 2017 for offering donors favors in exchange for contributions to a nonprofit controlled by his allies, the Campaign for One New York.