According to new research babies who sleep in their parents' bed are at increased risk of cot death even if their mother and father are non-smokers.
The study also says that an adult sleeping with a baby on a couch or chair puts the child at increased risk.
While it has been acknowledged for some time that babies are at increased risk if their parents are smokers, this is the first study to highlight the dangers for babies whose parents are non-smokers.
Over a four year period researchers from Glasgow University carried out a detailed analysis, using data from the parents of 123 victims of sudden infant death.
This study, which was an attempt to improve advice for parents worried about the condition, was funded by the Scottish Cot Death Trust (SCDT).
The study revealed that babies under 11 weeks of age who are taken into bed to sleep with parents even if the parents are non-smokers and the child is breast-fed, are at increased risk of cot death.
The findings, have now been added to advice leaflets which recommend babies are kept out of the parental bed for their first six months.
Dr John McClure, SCDT chairman, says that until recently it was thought that bed-sharing was a risk only if parents were smokers, but this new study confirms a significant risk for young babies, whether or not parents smoke.
He says they are now advising parents especially in the first three months of life, that while it's fine to have the baby in bed to feed or cuddle, the baby should be placed back in their own cot, in the parents room, before the parent falls asleep.
After the first three months of life that risk diminishes sharply.
Between 350 to 400 cases of unexplained cot deaths are reported each year in the UK, and a total of 29 occurred in Scotland last year.
The investigation was carried out between 1996 and 2000, by interviewing the parents of 123 babies who died.
The researchers gathered information on areas such as feeding habits, care routines and how the babies slept.
They also created a control group of 263 babies and their parents who were asked the same questions.
The study found that 11 per cent of the babies that died slept in their parents' beds, compared to five per cent of the babies in the control group.
But the researchers also discovered that 52 per cent of the babies that died spent at least part of their final night in their parents' bed, while only 20 per cent of the control group parents gave the same answer for the previous night.
Hazel Brooke, SCDT executive director, who was part of a "highly experienced" team which conducted the project, says they learned that a lot more babies sleep beside their parents than was previously thought, and the findings clearly demonstrate that there was a risk involved.
A Scottish Executive spokes-man says in order to reduce the risk of cot death, the safest place for babies to sleep is in a cot.
SCDT also advises parents to carefully place babies on their back to sleep, avoid smoking in their presence and keep their heads uncovered.
The findings are published in the Journal of Pediatrics.