After two years of research, the national Sleep Council is today calling for the end of the nine-to-five working day.

Experts have revealed that the natural sleeping pattern of the human race is not suited to the standard working day.

The Sleep Council, based in Skipton, North Yorkshire, published its survey results as Britain prepared to celebrate the seventh National Sleep-In Day on Sunday - the day the clocks go back and we all get an extra hour in bed.

More than 12,000 people responded to a sleeping habits questionnaire launched in 1999.

Thirty-eight per cent regarded themselves as better workers in the evening, while 41 per cent were more switched-on in the morning.

Dr Chris Idzikowski, who conducted the research, said: "By a showing a preference for morning or evening work, the implication is that the majority are not fully alert in the middle of the day.

"We must conclude from this survey that the traditional nine-to-five working day does not suit the majority."

Only 1.4 per cent of people were bothered by their partners' cold feet, while just 2.3 per cent complained of being awoken by "amorous behaviour".

Sex gained universal recognition as a sleep aid, with 37 per cent of those questioned mentioning it as a handy prelude to a good snooze.

Britain was also exposed as the most scantily clad of nations at bedtime - with 51 per cent going naked in summer, but just 29 per cent sleeping au naturel in winter.