Police chiefs have accused parents of being naive and complacent about the widespread use of cannabis among teenagers.
The Association of Chief Police Officers said adults did not understand that new, more potent forms of the drug were available, and harming young people.
The body was speaking out after a mother was sentenced this week for giving her children cannabis to stop them buying the drug from street dealers.
Assistant Chief Constable Simon Burne said: 'I think frankly there is a group of parents that are complacent and turn a blind eye to drug use in the sense of 'out of sight, out of mind'.
'In turning that blind eye, they are creating a deeper mess because we are worried about the rise in potency of the cannabis that is on the streets.'
Drugs spokesman Mr Burne, from Merseyside Police, said ACPO was reviewing its stance on lobbying for cannabis to be upgraded from a class C drug, but his personal view was that it should become a class B substance, as it was up to five times stronger than in the 1980s.
He said studies showed around one in five teenagers had tried the drug 'as part of their life experience'.
Mr Burne added: 'A key message today is about the harm that cannabis can cause, and the need for better education both for young people and their parents.'