A new study has found that women in red are regarded as better looking and more desirable to men - in fact, this is driven by nothing but primal instincts that associate the colour with sex.

According to lead researcher Prof Andrew Elliot, the study aims to provide hard evidence of "society's enduring love affair with red".

"Although this 'red alert' may be a product of human society associating red with love for eons, it also may arise from more primitive biological roots.

"It could be this very deep biologically based automatic tendency to respond to red as an attraction cue given our evolutionary heritage," Prof Elliot was quoted by British newspaper The Daily Telegraph as saying.

The researchers from the University of Rochester came to the conclusion after carrying out an experiment, involving over 100 men who were shown photographs of a "moderately attractive" young woman.

The subjects, mostly university undergraduates, were shown the pictures and asked to rate how pretty they were, how much they would like to kiss them and how much they would like to have sex with them.

The men were shown a woman, with some of the pictures bordered in red and some in white, gray or green. Even though it was the same picture the males rated her as more attractive when bordered in red than by another colour.

Other photos showed a woman in different colours of shirts and again red scored strongly. It was also estimated they would spend almost twice as much on her if she was dressed in red compared to her in blue.

Despite the effects, the men also insisted colour played little role in their choices, which would suggest they were unaware of the power of red.

The study has been published in the latest edition of the Journal of Personality and Social Psychology.