Citing concerns about potential voting irregularities during the most consequential presidential primary in years, the New York City comptroller, Scott M. Stringer, said on Tuesday that his office would audit the city’s Board of Elections in part to determine if tens of thousands of Democratic voters were improperly removed from voter rolls.

Mr. Stringer said in a statement that the Board of Elections had confirmed that more than 125,000 Democratic voters in Brooklyn were dropped between November 2015 and this month. He said the decline occurred “without any adequate explanation furnished by the Board of Elections.”

“There is nothing more sacred in our nation than the right to vote, yet election after election, reports come in of people who were inexplicably purged from the polls, told to vote at the wrong location or unable to get in to their polling site,” Mr. Stringer, a Democrat, said.

On Tuesday, Mayor Bill de Blasio, also a Democrat, echoed Mr. Stringer, noting that voters and voting rights monitors had reported the “purging of entire buildings and blocks of voters from the voting lists.”