A city watchdog is threatening “legal action” against the NYPD for failing to cooperate on a probe the City Council called for last year.

In 2017, Mayor Bill de Blasio signed a law requiring the NYPD’s Inspector General to analyze allegations of police misconduct, including lawsuits. But the NYPD has refused to make key personnel available for interviews and provide certain information, according to an Inspector General report released Monday.

The report indicates that the Department of Investigation — in which the Inspector General's Office is a unit — is in negotiations with the NYPD regarding “these and other non-disclosure issues.”

“In the event that DOI determines that such negotiations are not reasonably likely to succeed, DOI will notify the City Council of such impasse and will take appropriate legal action,” according to the report.

The NYPD has had a contentious relationship with its Inspector General since the watchdog agency was formed in 2014. In 2015, the NYPD upstaged the release of an Inspector General report on use of force — holding its own press conference the same day to announce new rules governing its deployment.

In March, the Inspector General released a damaging report showing the department doesn't put enough resources into investigating adult sex crimes. The NYPD put out a scathing response — prompting an Inspector General response to the response.

The Department of Investigation declined to comment beyond what’s in the report.

"The NYPD welcomes the conversation on civil lawsuits and is constantly striving to improve," Det. Kellyann Ort wrote in an email to WNYC.