The rise includes people lured to the country after meeting people via online dating or job recruitment siteschina virtual office.
Romania remains the most likely country of origin for victims, followed by Poland and the UK.
The NCA says trafficking does not have to involve crossing international borders.
Investigators say the rise is partly down to better reporting, including an increase in the number of children feared to be victims of sexual exploitation gangs.
False benefit claims
Overall, the agency says there has been a 22% jump in the number of identified suspected victims of trafficking between 2012 and 2013.
The 2,744 suspected victims, thought to be the tip of the iceberg, include 602 childrenSim .
The NCA says there has been a surge in reports of sexually exploited children - from 38 to 128 - in the wake of high-profile abuses cases in Rotherham and elsewhere.
Investigators also found cases of adults forced into prostitution, labour exploitation, domestic servitude, or compelled to commit crimes such as making false benefit claimshair loss treatment .