In research for the NSPCC, 64 per cent of UK adults said they would be concerned about being wrongly suspected or that someone would misunderstand their intentions if they went to the aid of a youngster who seemed to be lost.
Nearly half of the 2,899 respondents (45 per cent) said they would stay close by and observe - almost as many as those who said they would approach the child (47 per cent). More than one in three of those polled said they had been in that situation.
Fear of being wrongly accused or someone misreading their intentions was the most frequently cited barrier to approaching a child.
Meanwhile 44 per cent of respondents said they are more likely to report suspected child abuse following high profile cases.
But if they thought a neighbour's child was being neglected or abused, 62 per cent admitted they would be worried about reporting it as they fear making a mistake.
Peter Watt, director of the NSPCC helpline, said: "Taking action is always the right thing to do - whether it's a lost child in the street or an abusive neighbour."
The charity urged people to use its helpline if they are unsure about what to do.