NYPD sergeants were urged by their union chief on Wednesday to not answer questions from Bronx prosecutors about their disciplinary records and mental health — and instead turn the tables by asking about the sex-and-booze scandal in the District Attorney’s Office.

Sergeants Benevolent Association President Ed Mullins issued a memo saying he “was just informed by members of the SBA Board of a new policy instituted within the incompetent Bronx District Attorney’s Office.”

Bronx DA’s spokeswoman Patrice O’Shaughnessy said the NYPD sent out a bulletin alerting cops that prosecutors would question them to find out if they were vulnerable to damaging cross-examination but added: “Police officers would never be asked about . . . disabilities.”