The ASA complaints board noted the word and its variations appeared as the third, fourth, sixth, seventh and eighth most offensive expletives out of 31 in the Broadcasting Standards Authority 2013 survey.
It said the advertisement was likely to cause serious and widespread offence in light of generally prevailing community standards and upheld the complaint.
The campervan rental company had previously raised eyebrows over other colourful advertising that sparked complaints to the ASA.
One newspaper advertisement in 2011 featured an image of a mountain and a person inhaling a mound of white powder, along with the words: "Wicked 100 per cent pure New Zealand."
A complaint said the ad associated New Zealand with cocaine use.
In 2010 a slogan on the back of a van reading "if you love me you would swallow it" was ruled offensive by the authority.
Meanwhile, the authority found a programme claiming "guaranteed weight loss" without any qualification was "socially irresponsible".
A flyer and signage for weight management company Miraculoss claimed up to 10kg of weight loss in three weeks and reshaping of "problem areas" with no exercise.
Complainant M Honeyworth told the ASA there was nothing on the company's website to back up the science-based claims.
Miraculoss said it had changed the wording on its ads, including removing any reference to a product and emphasising the weight loss programme.
The complaints board upheld the complaint and said the original messages were socially irresponsible.
