A woman injured in a crash was initially told by police they could not act because the collision only involved a pedal cycle.
Stephanie Skinner, 18, was hit by a cyclist on the pavement outside the pet shop where she works in Stockport, Greater Manchester, on 4 December.
Police said it could not be classed as a road traffic collision as it did not involve a motorised vehicle.
Ms Skinner’s Labour MP Ann Coffey took up the case and police have now reversed their decision.
A spokesman for Greater Manchester Police said: “This decision was reviewed and the incident is now being investigated as an offence of riding a cycle on a road, bridle way or footpath without due care and attention, contrary to Section 29 of the Road Traffic Act 1988.
“Officers have identified a suspect and inquiries are ongoing.”