An off-duty NYPD officer was critically injured after losing control of his electronic bike in Brooklyn Thursday afternoon.

The cop crashed into a parked vehicle on Clarendon Road near East 31 Street in Flatbush just before 4 p.m. and suffered a head injury, according to law enforcement sources.

He was not wearing a helmet, the sources said.

The officer was taken to Kings County Hospital in critical condition, according to the sources.