A police officer who was videotaped knocking a man off his bicycle and onto the ground during a cycling event in Manhattan last summer has resigned, the Police Department said.

Paul J. Browne, the Police Department’s chief spokesman, said the officer, Patrick Pogan, 23, resigned about 10 days ago.

Mr. Pogan was accused last year of assault and of filing false paperwork related to the arrest of the cyclist and was suspended from the department. The Manhattan district attorney’s office dropped the charges  attempted assault, resisting arrest and disorderly conduct  against the cyclist, Christopher Long.

Mr. Browne said on Thursday that the firing stemmed directly from the events involving Mr. Long, which took place on July 25 during a monthly event known as Critical Mass, in which hundreds of cyclists ride through the city to advocate nonpolluting forms of transportation.