Leading Green Party member Jenny Jones is recovering after being knocked from her bicycle at the Elephant & Castle.
The Southwark councillor, who also sits on the London Assembly, broke a wrist in a collision with a car one evening last month. She was on a cycle crossing when a car clipped her back wheel.
News has been slow to emerge as Police did not attend. But an ambulance was called to take Cllr Jones to St Thomas' Hospital where a metal plate has been inserted in her left lower arm by surgeons.
Speaking from Dorset, where the pro-cycling campaigner is convalescing with her daughter, Jenny Jones said: "Motorists have got used to just pulling away when the lights go amber but they shouldn't. They should wait until the light is green. Drivers are just so determined not to let anything hold them up.
"It makes me angry when I see cyclists go through red lights. I never do. It just annoys motorists and puts cyclists' lives at risk."
Jenny Jones, who will have her arm in plaster for six weeks, hopes to return to work part-time.