That is not what the theory of relativity says at all. The special theory of relativity has two conjectures (I'm not going to go into the general theory here): 1) The laws of physics are constant in all inertial reference frames, and 2) the speed of light is constant regardless of the motion of the observer.
If you want to take this to a logical conclusion you will find that it will take an infinite amount of energy to accelerate any object to the speed of light.
Well, I have Einstein's book right here, his Stafford Little lecures, with appendices, so if we have any questions we can possibly get at least a clue from that. Probably the important thing is that it refers to electromagnetism.