Police chiefs are accusing parents of showing ignorance and complacency in the face of widespread cannabis use among teenage children.
Cannabis can be three times as strong as it was 30 years ago
The Association of Chief Police Officers says many parents do not understand the serious health risks of newer, more potent strains of the drug.
It is calling on parents to show zero tolerance to help stamp out use of the class C drug.
Government figures for 2006 suggest one in 10 under-16s has smoked cannabis.
The call follows the sentencing of mother Nicola Cooper earlier this week for giving cannabis to her children to stop them buying it from street dealers.
Assistant Chief Constable Simon Byrne of the Association of Chief Police Officers (Acpo) said it was irresponsible parenting to introduce drugs to children.
"It's about zero tolerance," he told BBC Breakfast News.
"It's not cool to smoke drugs. You are not being a good parent by introducing drugs in any sort of way to children's experience to help them grow up.
"It's harmful, there's no place for it so stamp it out."
Glen Smyth, chairman of the Metropolitan Police Federation, said parents who may have smoked cannabis recreationally in their university days are misguided about the health dangers.
FACTS ABOUT CANNABIS
Cannabis was reclassified from a class b to a class C drug in 2004
It is often imported but is increasingly cultivated in UK homes and greenhouses
Short-term effects are increased pulse rate, decreased blood pressure, bloodshot eyes, heightened appetite and dizziness
In the longer term, smoking it can lead to lung damage, paranoia and mental health problems
Department of Health figures suggest the number of under-16s trying the drug has fallen in recent years
It is thought cannabis can now be three times as strong as it was 20 or 30 years ago.
"We need to get rid of the idea that cannabis is really OK," said Mr Smyth.
"What is largely unseen are our psychiatric hospitals full of people whose illnesses have been triggered by cannabis."
He said it was important to get the message across to children at junior school age of the downsides of the drug.
The police have the support of some health professionals who fear the potency of different types of cannabis, including skunk, is misunderstood.
Professor Robin Murray, of the Institute of Psychiatry, said parents needed to think of cannabis in the same way as they would about alcohol.
"Some liberal parents have been quite pleased when their 15-year-olds tells them they are taking cannabis. They say 'oh, thank goodness' they are not drinking.
"Some kids are taking the equivalent in cannabis terms of what would be a bottle of vodka a day."
Charity Drugscope agrees that some parents are complacent, but insists there are many who are very concerned about their children using drugs.
Martin Barnes, Drugscope's chief executive, advised worried parents to stay calm, seek reliable information and to talk to their children.
"The important point for parents is not to overreact," he said.
"Just because a child is using the drug, they might be experimenting as many young people do, doesn't meant they are going to become a long-term user or a problem user."
But Debra Bell, whose son started smoking cannabis at 14, told BBC Breakfast News that had not been her experience.
Her son's behaviour became increasingly aggressive and unpredictable and eventually led to him making himself homeless.
She said the received wisdom was to apply tough love but it had been a difficult decision to make.
"I still can't believe we have lost our son all from this so-called soft recreational drug," she said.