They said offence was a subjective matter. However, they disagreed that the ad was likely to cause serious or widespread offence.
It said that the ad only appeared in one location, which was within the boundaries of a pub car park. They said the poster was not in close proximity to a school or residential area.
The ASA accepted the complaints and banned the ad.
A spokesman said: "The ASA noted the ad was for an adult entertainment venue and, as such, the image was relevant to the nature of the club being advertised.
"We noted that FC said the model was gender neutral but given the prominence of the breasts in the image, particularly in conjunction with the text "Join the FILLIES girls ...", we considered consumers were likely to view the torso as being that of a woman.
We considered the ad presented the model as a sexual object and considered that, particularly in conjunction with the references to "FILLIES" it was likely to be seen as objectifying women and demeaning them.
"We considered the model's pose and dress were sexually provocative and had the effect of making the model appear sexually available.
"Although we acknowledged the imagery in the ad was relevant to the nature of the venue being advertised, we considered it, in particular the main image of the model, was overtly sexual and was therefore likely to cause serious or widespread offence in an untargeted medium.
"We understood the ad was placed outside a station and approximately 0.2 miles from a primary school.
"Nevertheless, we noted it could to be seen by children, given that it appeared in an untargeted medium.
"We considered the ad was overtly sexual and therefore unsuitable to appear where it could be seen by children.
"The ad should not appear again in its current form.
"We told FC to ensure future marketing communications were prepared with a sense of responsibility to consumers and society and that, particularly in an untargeted medium, they did not contain anything that was likely to cause serious or widespread offence."