Parents may be putting newborn babies at risk, a charity has warned, after a survey found many were happy to let their baby sleep on their stomach or side.
The Lullaby Trust said around half of parents are unsure of basic steps they can take to reduce the risk of sudden infant death syndrome (SIDS).
SIDS, also known as cot death, is the sudden unexplained death of an apparently healthy baby.
It hit the headlines in 1991 after TV star Anne Diamond's son Sebastian died in his cot.
She launched a sleep campaign in light of research showing that babies were far less likely to die if they were put to sleep on their backs.
But the Lullaby Trust is concerned that some parents are unaware of or ignore this message, while others do not know about the risks of drinking and sharing a sofa with a baby, or smoking.
It polled 500 parents of children under two and found that while 94% had heard of SIDS, 15% thought it was fine for children to sleep on their tummies while a further 23% neither agreed or disagreed with this.
Some 62% disagreed with the idea that it was fine for babies to sleep on their tummies.
One in four parents also thought it was fine for babies to sleep on their sides while 45% disagreed and 30% neither agreed or disagreed.
This is despite 87% being aware that putting a baby on their back for every sleep reduces the risk of SIDS. Doing so reduces the risk of SIDS six times.
There were 230 sudden infant deaths in the UK in 2014, following a downward trend in the last decade. In 2001, there were 330.
The Lullaby Trust says babies should be put to sleep on their backs in a cot that is free of bumpers, toys and pillows.
Francine Bates, chief executive of the charity, said: "Twenty-five years after the Back to Sleep campaign, the survey results have shown us we need to go back to basics."
Robert Weeks, who lost his daughter Sophia to SIDS, said: "On January 3 2012 our lives changed forever when our beautiful daughter Sophia died suddenly and unexpectedly.
"She was just about to turn 11 weeks old.
"We have still never had an explanation for why our healthy and 'normal' daughter died. We were one of 221 families that year whose child died for no apparent reason and with no cause found, even after a post-mortem was held.
"I think the work that The Lullaby Trust does to raise awareness of safer sleep for babies is absolutely vital. Every new parent should be made aware of this information if it will prevent other families from going through what we have been through."