Children in Hertfordshire committed more than 150 drug offences last year, official figures show.
It comes amid police warnings about the effects of county lines drug gangs on all police force areas in the country.
There were 156 drug offences committed by children aged between 10 and 17 in Hertfordshire in the 12 months to March 2018, Ministry of Justice figures show.
Only proven offences are counted, when a child receives a caution or sentence for the crime.
Not all crimes committed by children will lead to a formal outcome, meaning the actual number of crimes could be higher.
Some may be dealt with informally, such as being given a community resolution or referral to a Youth Offending Team for advice about their behaviour.
The number of offences in Hertfordshire fell compared to 2016-17, when there were 192.
However, across England and Wales the number of drug offences committed by children rose by 2.5% last year to 5,965 - the first increase for ten years.
A surge in county lines drug networks - which gangs use to transport drugs from urban centres into smaller towns and rural areas - has been blamed for the increase.
The Children's Society says gangs often target and exploit vulnerable children, such as those living in poverty or in care, to act as drug mules.
It is important that such children are supported as victims rather than criminalised, they added.
Iryna Pona, policy and research manager for the charity, said the increase in child exploitation could be behind the rise in convinctions and cautions.
"After being groomed through promises of cash, drugs and a glamorous lifestyle, children are then terrified into following orders and carrying out drug-related crimes," she said.
"We have sadly supported children who have been stabbed, raped and tortured, with their activities monitored through mobile phone live streaming and tracking.
"We want police to recognise that in many cases young people haven’t made a choice to get involved in gangs - they have been groomed and coerced in the same way as we have seen young people groomed and coerced into sexual exploitation."
The National Crime Agency estimates around 10,000 children as young as 11 years old are now being used as drug mules for county lines gangs.
The gangs use dedicated mobile phone lines to take orders and move drugs across their networks.
A new report by the NCA revealed there are now 2,000 such phone lines across the UK - up from 720 a year ago - facilitating around 1,000 unique drug trafficking routes.
Deputy Assistant Commissioner Duncan Ball, National Police Chiefs’ Council lead for county lines, said: "Police forces across the UK are working together to dismantle these networks and protect the young and vulnerable people who are exploited by them.
“The work of the National County Lines Co-ordination Centre has resulted in more arrests and large amounts of drugs and weapons taken off our streets.
"We will continue to do all we can to pursue and prosecute those who commit violence and exploit the vulnerable.”
Drug offences made up 12% of all proven child offences in Hertfordshire last year.