Brisbane-based Wicked Campers was found to have made light of abduction by splashing the slogan "Fat chicks are harder to kidnap" on one of its vehicles.
The Advertising Standards Bureau has upheld a complaint that the company breached Section 2.6 of the Advertiser Code of Ethics, which states that advertising or marketing communications should not depict material contrary to prevailing community standards on health and safety.
The board's judgement noted that "there is significant community concern regarding kidnap, especially in light of current high profile cases involving the abduction and murder of children both in Australia and overseas".
It added that "kidnap is illegal and ... this advertisement is making light of, and encouraging, behaviour which is against prevailing community standards on safety".
However, the bureau rejected the other reason for complaint – that the slogan was misogynistic and offensive to women.
The judgement noted the reference to "fat girls" and considered that the statement was general and not directed at a specific person.
"The board considered that the reference to fat girls in this instance, whilst tasteless and not a nice reference, does not meet the threshold for being discriminatory or vilifying towards overweight females or to females in general," the judgement read.
"The board considered that the advertisement did not depict material that discriminated against or vilified sections of society."
Wicked Campers has a history of tagging its campers – which are popular with backpackers - with gross-out humour.
Other slogans have included "Save a whale, harpoon a Jap", "Save a tree, eat a beaver", and "If God were a woman would sperm taste like chocolate?"
Brisbane Times has approached Wicked Campers for comment.