Waitresses who wear red get up to 26 per cent extra in tips than they would wearing other colours, researchers claimed.

However, the team that the sexes tip very differently - with the bigger tips coming only from male customers.

No matter what colour they wear, female diners will give the same kind of amounts for service every time.

Yet men, whether they realise it or not, add anything between 15 and 26 per cent more to a waitress in red than they would if it was the SAME waitress wearing a different colour.

The test was simple. Take 11 waitresses in five restaurants over a six week period and ask them to wear the same kind of tee-shirt every day but alternate the colours.

Previous research has suggested waitresses could earn more if they acted provocatively or wore more make up than their colleagues.

But this study, by the Journal of Hospitality and Tourism Research, only changed the colour of the tee shirt. Every other aspect from make up to behaviour remained the same.

When wearing either black, white, green, blue or yellow tee shirts, the size of the tips from both male and female customers was almost identical.

But when they wore red, the size of the gratuities went up by between 15 and 26 per cent from male customers, yet stayed the same from female ones.

A total of 272 restaurant customers were studied by researchers Nicolas Gueguen and Celine Jacob for the international journal of the tourism industry.

Even as a tee shirt, it shows just how much the colour red is perceived, by men, to increase the physical and sexual attractiveness of women, said the researchers.

And yet it did confirm some fears that it would make female customers react negatively and tip less for their gratuities remained at the same level throughout the study.

The researchers wrote: 'As red color has no negative effect on women customers, it could be in their interest to wear red clothes at work.'

The team previously found that slapping on red lipstick can also improve tips.They found customers are two-thirds more likely to leave a gratuity to waitresses with luscious red lips. Providing, that is, those customers are men.

The sociologists from the Universite de Bretagne-Sud, France, tracked the tips left for seven waitresses over two months against the variously coloured lipsticks they wore.

In almost 450 transactions, waitresses wearing pink or brown lippy, or none at all, got tips on average about 30 per cent of the time.

But when the waitresses put on red lipstick, male customers tipped half the time - and left more money. There was no significant change among female customers, however.