A complaint about a flier advertising Cosmic Corner's party pills, that a five-year-old had read, has been upheld by the Advertising Standards Authority.
A woman complainant wrote to the authority about the mailer sent to Wellington households that included brightly coloured cartoon rainbows, mushrooms and a bus.
"It is like a cross between Hi-5 and the Wiggles. You can imagine how unimpressed I was when my five-year-old came skipping in with the leaflet shouting `look at all this cool stuff mum," the complainant wrote.
Cosmic Corner, a retailer which sells party pills, responded that its branding was designed to appeal to adults who were "young at heart".
New Zealand Post's legal team had approved the fliers before it delivered them, it said in its response.
However, the authority upheld the complaint, saying the board unanimously held the view that the ad did not observe the high standard of social responsibility to consumers.
National MP Jacqui Dean said she was pleased the complaint had been upheld because this type of advertising sent the wrong messages to children.
"It is extremely concerning to see retailers still using images designed to be attractive to young children to sell mind-altering substances," she said.