Widening federal and local probes into Mayor Bill de Blasio’s fundraising methods are focusing on his failed 2014 effort to help Democrats seize control of the Republican-led State Senate, according to a published report.

Grand jury subpoenas were served this week demanding information about money raised for Democratic candidates in six or so races in play two years ago that de Blasio hoped to influence, according to a New York Times story Wednesday.

De Blasio’s chief City Hall spokeswoman, Karen Hinton, said Wednesday she didn’t know anything about the latest reported probe, and referred inquiries to de Blasio’s longtime campaign spokesman, Dan Levitan.

“We are confident that at all times all of our efforts were appropriate and in accordance with the law,” Levitan said in a statement.

The investigations did not come up during a town-hall-style meeting de Blasio held on Staten Island Wednesday night. The mayor instead focused on street paving, panhandlers at a ferry terminal and other municipal issues.

During the 2014 campaign season, de Blasio dedicated resources and political capital for Democrats to retake the Senate chamber, which along with the governor and Democratic-led lower house, controls much about what New York City can and cannot do, including who controls schools, nearly all taxation, and even the speed limit.

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For weeks, de Blasio has been buffeted by the widening investigation into his campaign finances. The mayor has neither been charged with any crime nor accused of any wrongdoing.

Government prosecutors are investigating whether de Blasio funneled money from smaller county political committees to candidates in races he hoped to influence in an effort to avoid restrictions on the amount donors can give, according to the Times story.

County party committees don’t have the donation limits that candidate committees do.

The mayor used methods that may be legal but are questionable, said Dick Dadey, executive director of the Manhattan-based good government group Citizens Union.

“It is troubling,” Dadey said, “but it’s a practice that has been employed in the past. But it’s just one more indication of how corrupt our campaign finance system is.”

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Several governmental agencies, including the city comptroller, the city Department of Investigation, the NYPD, the state attorney general and the U.S. Attorney’s Office for the Southern District of New York are probing one or more aspects of activities involving de Blasio, his causes, donors or some combination.

Sources have said investigators are looking at donations to a nonprofit set up for the mayor to further his policy agenda, a nonprofit that isn’t hindered by donation limits to political candidates.

A land deal involving the almost unheard of removal of a restrictive deed on a former AIDS housing property that was then sold and converted into luxury condominiums is also under investigation. A top de Blasio fundraiser, James Capalino, played a lobbying role in the deal.

Wednesday night, The Wall Street Journal reported that probers have also begun examining the mayor’s controversial, and so far failed, attempt to ban horses from Central Park, and the donors who gave to his mayoral campaign in an effort to push de Blasio to enact the ban.