PITTSBURGH — The city’s police union is surveying officers about Chief Cameron McLay ahead of a no-confidence vote planned for next month.

The Fraternal Order of Police, Fort Pitt Lodge No. 1, which represents most of the nearly 900 city officers, has clashed with McLay since he took the job in 2014. Among other things, McLay has been criticized for addressing the Democratic National Convention in uniform.

Although the chief defended his remarks as nonpartisan and meant to stress the need for better police-community relations, the union says the appearance violated a conduct policy in which police cannot participate in politics in uniform. McLay called for the city’s Office of Municipal Investigations and the Citizens Police Review board to determine if he violated the policy.

OMI and the review board investigate allegations of police misconduct and usually act on complaints filed by citizens or other outside agencies. Both are empowered only to make nonbinding disciplinary recommendations.