Researchers at University College London claim to have found the first physiological evidence that subliminal images can attract the brain's attention on a subconscious level.

The research suggests that techniques such as subliminal advertising, banned in the UK but still legal in the US, can actually have an effect.

The scientists found that an image which reached the retina still had an impact on brain activity even when the subject was not conscious of having seen the image.

Bahador Bahrami, of the UCL Institute of Cognitive Neuroscience and the UCL Department of Psychology, said: "What is interesting here is that your brain logs things that you are not aware of and cannot ever become aware of.

"We showed that there is a brain response in the primary visual cortex to subliminal images that attract our attention without us having the impression of having seen anything.

"These findings point to the sort of impact that subliminal advertising may have on the brain. What our study does not address is whether this would then influence you to go out and buy a product.

"I believe that it is likely that subliminal advertising may affect our decisions, but that is just speculation at this point."

Bahrami claimed that the findings challenge the previous assumption that what is subconscious is also automatic, effortless and unaffected by attention.

"This research shows that when your brain does not have the capacity to pay attention to an image, even images that act on our subconscious simply do not get registered," he said.