Parents in Melbourne and Sydney are endangering the mental well-being of young children by giving them cannabis as a sedative, a leading youth worker claims.

Prominent Melbourne social worker Les Twentyman says the worrying practice continues to become more prevalent in "impoverished" areas of Melbourne, just as it is in struggling Sydney suburbs.

He said parents unable to afford medication for children, particularly those with behavioural problems, often thought their own drugs could be a solution.

"I know of occasions when they have issues with their neighbours complaining about their kids screaming," Mr Twentyman said.

"To try and keep their own kids quiet for their own sanity and the neighbours, they have resorted to giving the kids drugs."

Children as young as six had been affected by either smoking bongs or through inhaling smoke in the air.

"I remember once walking into a flat where there were three mothers smoking bongs and they had five children," he said.

"They said to me: 'Look at how well behaved our kids are'.

"I almost fell over. Those kids had been affected by the cannabis in the air.

"The parents think it's a quick fix, but it's the start of a life of long-term misery."

Mr Twentyman said it generally was in high areas of unemployment where children were most susceptible.

"It's in the impoverished areas - in west Melbourne, outer southern areas, and also the multi-complex areas, the ministry-of-housing areas," he said.

Mr Twentyman said more was needed to be done to educate parents about the long-term dangers of giving drugs to children.

"The linkage between that and mental issues later on is very significant," he said.

"It's about education and access and having an enormous amount of support, getting youth workers attached to schools and high-rise flats and things like that.

"I would like a television and newspaper campaign like the TAC (Transport Accident Commission in Victoria) about the long-term effects on young people whose minds aren't probably developed because of drugs."

Mr Twentyman's comments come after counsellors from a leading Sydney children's charity, the Ted Noffs Foundation, told the Sunday Telegraph newspaper there was a growing trend of parents in western Sydney suburbs giving their children cannabis.

- AAP