The “multiple investigations” of Mayor de Blasio are one reason state Senate Majority Leader John Flanagan won’t agree to extend mayoral control of the city’s public schools for more than a year.

“In light of the questions that remain over how Mayor de Blasio intends to lift up failing schools . . . not to mention the multiple investigations into the mayor and his administration — I have deep reservations over signing off on a longer extension,” Flanagan said in a statement Monday.

Because of Republican resistance, the Legislature and Gov. Cuomo last year agreed to a one-year extension. It expires June 30.

By comparison, former Mayor Mike Bloomberg had six years.

A one-year deal would force the mayor to return to Albany next spring — right in the middle of his re-election campaign.

City Hall spokesman Austin Finan said the state Senate was playing politics.

“It serves no one to hold our children’s educational progress hostage. Once again, we urge the Senate to put students before politics,” he said.