The International Cycling Union (UCI) said it was "extremely unhappy" with the poster which shows a hand moving towards a girl's backside.
"We have reminded the organiser of its responsibility," said a UCI statement.
The poster mimics the antics of 2014 winner Peter Sagan who pinched a podium girl at the 2013 Tour of Flanders.
Although the UCI press release states that organisers have agreed to remove the poster, which also carries the tagline, 'Who squeezes them in Harelbeke?', it is still being used to promote the event on social media.
In 2014 UCI president Brian Cookson described a cycling team's kit as "unacceptable by any standards" after it appeared to make the female riders look naked.
Photos of the Colombian team's outfit for the Giro della Toscana in Italy showed what seemed to be a skin-coloured fabric around their waist and hips and caused controversy on social media.
The E3 Harelbeke, which is on 27 March this year, starts and finishes in Harelbeke and covers 210kms of the Flanders region.
The race is part of the UCI World Tour and is regarded as a preparation for the  seven Spring Classics which include the Tour of Flanders..
Cycling's governing body has condemned E3 Harelbeke organisers for a controversial billboard poster that promotes this year's race in Belgium.