"Domestic trafficking of children for sex is a sophisticated type of exploitation, a sinister form of organised violation through networks of criminals.
"Nobody currently knows the full extent of these crimes because of their hidden nature, but what we do know is that every time we open a new service for victims it quickly becomes fully subscribed.
"If we are to save children from suffering for years at the hands of their abusers, more must be done by the authorities to identify victims of child sexual exploitation who are being internally trafficked and to stop this activity earlier on."
The charity surveyed 23 of its specialist services, an annual report it compiles each year.
Barnardo's service data also revealed that numbers of sexually exploited children helped by the charity rose by 377% in Wales, from 22 to 83, where the charity has become more active.