More than 50 sex offences involving adults in a position of trust have been recorded in the North East and Cumbria since 2011-12, data shows.
Home office figures show that there has been a 57% rise in offences for Abuse of Position of Trust in England and Wales over that period.
The offences analysed involved professionals such as teachers or care staff who had sexual contact with 16 or 17-year-old children they worked with.
In the Northumbria Police force area, there have been 24 such offences since 2011-12, while the figures are 12, 10 and seven for Cleveland, Cumbria and Durham respectively.
Children's charity the NSPCC, though, fear the true extent of abuse is much worse.
The law does not apply to youth work roles such as sports coaches and leaders of religious groups.
The NSPCC is now calling for laws to be extended, to better protect children in sport and other youth activities.
NSPCC head of policy Almudena Lara said: “Safeguarding in children’s clubs should not end suddenly at 16.
"The NSPCC has been told of a number of cases where in sports and other youth work settings, leaders have used their position to groom children, and then take advantage of them as soon as they turn 16.
“It is baffling that sports coaches and other youth workers are not deemed to be in a position of trust, given the significant responsibility, influence and authority that adults in these roles have over the children they are there to look after.
“Sadly, we know that this trust can be abused and it is therefore vital that this legal definition is widened to include sports coaches and other youth workers, bolstering protection for teenagers at risk of grooming once they pass the age of consent.”
In England and Wales, 1,290 offences have been recorded since 2011-12.