Mayor Bill de Blasio Tuesday accused an NYPD union of "fear-mongering" by blaming its opposition to the city's bid for the 2016 Democratic National Convention on plummeting police officer morale and rising crime.

De Blasio said a letter from the union's president to the Democratic National Committee was an effort "to try and benefit their own opposition to labor talks."

The mayor made his comments in response to the letter Tuesday from Edward Mullins, the president of the 13,000-member Sergeants Benevolent Association.

Mullins wrote that "the great city . . . is lurching backwards to the bad old days of high crime, danger-infested public spaces, and families that walk our streets worried for their safety."

Among venues on a short list for the convention is Brooklyn's Barclays Center. City officials have said the event would bring in more than 30,000 visitors and pump hundreds of millions of dollars into the economy.

De Blasio took the lead two weeks ago as New York political leaders courted a DNC scouting team that toured Barclays Center and the city. NYPD Commissioner William J. Bratton assured the group the city could provide ample security, crowd control and safe and fast transportation.

In his letter, Mullins wrote that diminished support for the NYPD and de Blasio's granting of "a public platform to the loudest of the city's anti-safety agitators" is behind a 13 percent spike in shootings and a "degradation" of quality of life.

Overall crime citywide, however, has dropped 3.6 percent this year, and homicide rates have fallen 12 percent, according to NYPD statistics.

Tuesday night, Mullins told Newsday that by blaming the letter's harsh message on labor negotiations, de Blasio has "completely changed the topic by diverting attention to contracts."

The union has worked under an expired contract since July 2011.

NYPD officials distanced the department from Mullins' letter.

"Ed Mullins, in his role as a union leader, is entitled to his opinions but these opinions are not shared by the NYPD," department spokesman Stephen Davis said in a statement.

Other political leaders backed de Blasio and the city's bid. City Council Speaker Melissa Mark-Viverito "obviously disagrees with this distinctly negative view of New York" said a spokesman for the speaker Tuesday.

In a statement, Brooklyn Borough President Eric Adams, a former NYPD captain, called Mullins' letter "an inaccurate and frankly inane spewing of political vitriol, all at the expense of everyday New Yorkers, including the men and women of the NYPD whom he represents."

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