The city can force groups of 50 bike riders to get a parade permit, a judge ruled yesterday.

Manhattan federal judge Lewis Kaplan cited the “city’s substantial interests in safety, efficiency and traffic flow.”

The battle between bike riders and the NYPD began after more than 260 bicyclists were arrested during the 2004 GOP convention as they took part in so-called “critical mass” rides.

The lawsuit was brought by the Five Borough Bicycle Club, which now organizes about 250 mass rides a year.

Lawyers for the cyclists declined comment.

City attorney Mark Muschenheim said, “The court recognized that the policing of Critical Mass rides was not based on any attempt to infringe First Amendment rights, but rather stemmed from . . . bicyclists’ lawless behavior, which included intentionally blocking traffic, riding through red lights, and cycling the wrong way on both one-way and two-way streets.”