Behavioural evidence has shown that the perception of an object's handle automatically activates the corresponding action representation. The activation appears to be inhibited if the object is a task-irrelevant prime mug that is presented very briefly prior to responding to the target arrow. The present study uses an electrophysiological indicator of automatic response priming, the lateralized readiness potential (LRP), to investigate the mechanisms of this inhibition effect. We presumed that this effect would reflect motor self-inhibition processes. The self-inhibition explanation of the effect would assume that the effect reflects activation-followed-by-inhibition observed rapidly after the offset of the prime at the primary motor cortex. However, the results showed that the effect is not associated with modulation of the early LRP deflections. In contrast, the inhibition manifested itself in the later LRP deflections that we assume to be linked to interference in the processing of response-related aspects of the target. We propose that the LRP pattern is similar to what would be predicted from the negative priming explanation of the effect. The study sheds light on understanding inhibition mechanisms associated with automatically activated affordance representations.