Criminals are recruiting a rising number of teenagers to act as money mules to help them launder the proceeds of crime.
The number of cases of 14 to 18-year-olds who have allowed their bank accounts to be used to divert funds has grown by 73% in two years.
Banks are using the data, from fraud prevention body Cifas, to alert parents to the risks their children face.
Teenagers are being recruited to the illegal activity via social media.
Sports clubs, schools and colleges are also key recruiting grounds for criminals who want to move money through accounts to make it look less suspicious to banks. The youngsters are given a cut for allowing their account to be used. Often they ask no questions over the source of the money.
Most money mules are young men. Those who try to quit may be threatened with violence by the criminals who recruited them.
If they are caught, they could face prison, as well as future difficulties with their finances, such as having their bank account closed and finding it difficult to apply for credit in the future.
'I was a teenage money mule'
"Have you ever held £2,000 at once in your hand?" That was the line used to tempt Holly into becoming a money mule.
At the age of 17 and still at school, Holly (not her real name) was approached on Instagram, then Snapchat, by a person who promised to pay her a decent sum, if she let him use her bank account to move money.
"I just eventually gave in," she said.
Teenagers can open their first current account in their teenage years. The Cifas figures show that money mule cases last year among 14 to 18-year-olds rose by 20% on the previous year, and by 73% over two years, to 5,819.
Mike Haley, chief executive of Cifas, said: "The increasing use of social media means that young people have never been more vulnerable to becoming victims of fraud.
"Many youngsters are unaware of the devastating consequences that fraud can have on their future opportunities, and so teachers, parents and carers can play an important role here by ensuring young people have the necessary knowledge and skills to prevent them from unwittingly falling victim to fraud, or even become perpetrators themselves."
Banking trade body UK Finance is behind a new awareness campaign encouraging parents and guardians to look out for danger signs.
They include telling youngsters to keep bank details safe, telling them to be cautious of unsolicited offers of easy money, and looking out for signs of their child suddenly having extra cash, or becoming secretive, withdrawn or stressed.