An automatic vehicle theft prevention system (52) selectively enables an ignition system (22) of a vehicle (20). The system (52) includes an interrogator circuit (54) that generates and radiates an excitation signal (68). A transponder circuit (56) in close proximity to the interrogator circuit (54), and separate from an ignition key (48) of the ignition system (22), detects the excitation signal (68) and modulates the excitation signal (68) to produce the return signal (74) containing an identification code (76) for the transponder circuit (56). The return signal (74) is radiated from the transponder circuit (56) and received at the interrogator circuit (54). When a controller (58), in communication with the interrogator (54), detects the identification code (76) in the return signal (74), the controller (58) actuates a relay (60) to an enable mode to enable the ignition system (22).