Researchers at Liverpool John Moores University found babies who were exposed to twice as much light between 12pm and 4pm became better sleepers.

A group of 55 babies were monitored for three consecutive days at six, nine and 12 weeks old.

The team also found that babies who slept well at six weeks were likely to be a good sleepers at 12 weeks.

Report co-author Dr Yvonne Harrison said, from the School of Psychology at the university, said: "Sleep deprivation is a big problem for many new parents.

"This research puts forward one theory that may help babies and parents get a good night's sleep, which is good news for everyone."

Light monitor

She said one possible explanation for the link between light exposure and sleep is that higher light levels encourage the early development of the biological clock, which regulates a number of bodily functions, including the secretion of melatonin, an important factor in well-balanced sleeping patterns.

Parents taking part in the study, which is published in the Journal of Sleep Research, were asked to continue their usual routines while a light monitor was attached to their pram or cot.

A diary was also kept of their sleep and crying patterns.

The researchers found babies cried twice as much at six weeks, 40 minutes per day, than 12 weeks, 20 minutes per day.

Paul Connew, of Sparks, a medical research charity which helped fund the study, said it was good news for parents.

"The findings probably back up what many mothers instinctively know, spending plenty of time in daylight encourages babies to sleep at night.

'Good sense'

"But I think it will be reassuring to parents that there is scientific research backing up what they think.

"We would advise parents to take their babies out in daylight during the day."

Dr Neil Stanley, of the British Sleep Society and director of sleep research at the University of Surrey, said the study seemed to make good sense.

"Melatonin helps us sleep and it is well known that daylight suppresses it.

"We have evolved over time to sleep during the night and be awake during the day but young babies don't know this, they have to learn it.

"Spending time in daylight would certainly help them learn this pattern.