Tell-tale signs of child sexual grooming are being overlooked, a leading charity has warned.
Barnardo's said just two in five parents believed children were being sexually exploited where they live, despite the prevalence of the problem across the UK.
It urged parents, professionals and young people to be aware of the signs, which can include children going missing for long periods, regularly returning home late, appearing with unexpected gifts or associating with older teenagers or adults.
Anne Marie Carrie, the charity's chief executive, said: "This is a horrific and pernicious crime that everybody needs to be alive to. Vulnerable defenceless girls and boys, who crave love and attention, are groomed then abused in the most callous and calculated way, leaving them deeply traumatised and scarred for life.
"Yet victims continue to go unidentified as tell-tale signs are overlooked. I want mothers, fathers, professionals and young people to have the confidence in spotting these signs. The earlier abuse is identified, the earlier we can stop it."
The poll of more than 1,100 parents also found less than half of parents were able to spot the more subtle signs of children being exploited, such as regularly returning home late (43%).
One in four fathers said they do not feel confident that they would spot whether the relationships their child has are dangerous, compared with one in six mothers.
A report by the Child Exploitation and Online Protection Centre in June found that key agencies involved in child protection have failed to put in place "basic processes" to stop sexual abuse.
There were 2,379 offenders recorded since the start of 2008, mostly men aged 18 to 24, the study found.
ComRes interviewed 1,147 GB parents online between August 3 and 7 2011.