Is that cigarette lighter plug powering the radio?
How many watts is the radio? Thats really, really not a good idea. Sometimes a 25 watt radio can get away with it if you have a 10 or 15 amp fuse in the cigarette lighter socket, but those wires are not meant for the load being placed on them under TX. If its for receiving only thats one thing, but I really would run a set of wires to your battery if you plan on transmitting.