New mothers should be taught about the risks of sleeping with their babies to try to cut the number of babies who die from cot death, health officials said.
The National Institute for Health and Care Excellence (Nice) said families should learn about safe sleeping habits for babies to reduce the risk of sudden infant death syndrome (Sids).
About 250 babies die from Sids every year in England and Wales.
In new draft recommendations, Nice said that all parents should be made aware of the link between cot death and falling asleep with a baby up to the age of one.
Midwives, GPs and health visitors should also make parents aware that the risks are significantly higher if parents drink, smoke or take drugs, the guidance states.
Babies born prematurely or with a low birth weight are at an increased risk of cot death if they sleep with their parents.
"Falling asleep with a baby, whether that's in a bed or on a sofa or chair, is risky," said Nice's clinical practice director professor Mark Baker.
"It's imperative that all parents and carers know about the association between sudden infant death syndrome and falling asleep with a child under the age of one. This is especially important if parents drink alcohol, take drugs or expose their baby to tobacco smoke."
He added: "There is no universal agreement on the causes of sudden infant death syndrome.
"We know there is a link between Sids and falling asleep with a baby in a bed or on a sofa or chair, but studies into why this happens can often give conflicting results. And other factors are likely to play a part in increasing the risk to the infant.
"We recognise that some parents may choose to share a bed with their baby because it could make breastfeeding easier, or for cultural reasons. Or they may be forced to co-sleep because they may not have the space or money for a cot.
"This is why it's so important for parents to understand what the risks are. The recommendations we are developing aim to help healthcare professionals inform parents and carers of the likely risks associated with co-sleeping, according to the best available evidence."
The Nice guidance has been put out for consultation until the end of the month.
Belinda Phipps, chief executive of the National Childbirth Trust, said: "Parents need accurate, comprehensive information about reducing the risk of SIDS. It is important that they are informed about the link of co-sleeping with SIDS when combined with smoking, drug or alcohol use or for low birth weight or premature babies.
"However we know that around half of UK mothers bed-share with their baby at some point in their first few months.
"Nice guidance needs to reflect this reality. We are concerned that these guidelines will lead to parents hiding the fact that they are bed-sharing, or doing so through desperation or exhaustion without safety strategies in place."
Jane Munro, midwifery adviser at the Royal College of Midwives, said: "The sudden death of a child is a tragic event for the parents and family and it is clear that parents need to understand any potential risks.
"We welcome updating this guidance, particularly because it highlights the importance of health professionals discussing potential risks of co-sleeping with families. Midwives and other health professionals need to have enough time to discuss these important issues with families."
Dr Simon Newell, consultant neonatologist and vice president for the Royal College of Paediatrics and Child Health, added: "Every case of unexplained infant death is an absolute tragedy for a family, and although rare, still claims the lives of around five babies each week - that's still five cases too many.
"Most of the time co-sleeping is safe but the risk increases when an adult is very tired, drunk alcohol, used drugs or when they have taken medication which might sedate.
"To address this, we need to help ensure that all families have access to safe sleeping guidance and resources. And because we know that vulnerable families are especially at risk of Sids, we need a targeted campaign to promote safe sleeping habits.
"We hope these updated recommendations from Nice will raise awareness of Sids and remind us all that more can be done to prevent deaths in future."