C.Logan said that was "deeply offensive" and was an "objectifying, demeaning sexualisation of women."
She also said it demeaned women's roles on construction sites.
"As a woman who has worked in construction in the past, the already entrenched sexism faced daily is only worsened by the proliferation of this kind of advertising message in public spaces."
In a majority decision, the authority shot down the complaint.
The double entendre with the shadow was acknowledged, but the "risque" image was described as "subtle" and was covered by a provision in the industry code allowing for humour.
The humour within the shadow did not meet the threshold of causing serious or widespread offence, the authority ruled.
However, a minority view didn't agree and raised concerns the image was not socially responsible.
Gillman Wheelans director Hamish Wheelans said he and two staff came up with the ideas for the company's advertising and they're then tested on a focus group.
Other feedback on its advertising has been positive.
"I thought the complainant was taking it a little bit too far in what they are reading into it. It was about humour," Mr Wheelans said.
"Every time I see and ad and it's mum, dad and two kids. We try and inject a bit of humour and a bit of fun into our advertising, whether it's radio, press or billboard.
"Sometimes people like the ad. Sometimes they don't."
Mr Wheelans said the company didn't set out to offend anyone.
"A few people get offended by it. That's life. We are prepared to push the boundaries to what we think is reasonable."
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