DCP(Central) DP Singh was injured when BJP workers, who were demonstrating in front of Kolkata Municipal Corporation, hurled brickbats, police officials said.
The demonstrators were trying to break through a barricade put up by the police in front of the corporation, they said.
Five BJP activists were detained in connection with the incident, they said, adding that the situation was "under control".
BJP state Secretary Ritesh Tiwari alleged that the police attacked the BJP trade cell workers who were expressing solidarity with the agitating businessmen in the area.
Asked about the injury of the DCP(Central), he said BJP workers were not involved in it and demanded that there should be a thorough investigation to find it out.
TMC mayor-in council Atin Ghosh condemned the incident and alleged that BJP was trying to create chaos in the area.