The Australian Vaccination-skeptics Network has been forced to apologise for a black and white advert that compares vaccinations to rape, which appeared on a Facebook page linked to the group.
The photo was uploaded this week and was quickly criticised for comparing vaccination and violent sexual assault.
Moderators removed the photo from the page and issued a statement.
"The AVN has not owned this Facebook page for some time. This page is open to the public. We sincerely apologise for an earlier post that caused offense to many, including supporters," it said.
"We are still investigating and have taken your comments on board."
However, other anti-vaccination campaigners have hit back. One update on the same page angrily criticises the media's portrayal of the movement and questioned the definition of rape.
The page now directs people to the group's website and stresses that the Facebook page is moderated by volunteers.
The group was forced to change its name last year after the New South Wales Government found its original name, "Australian Vaccination Network" could mislead people into thinking it was pro-vaccination.
The anti-vaccination movement has recently grown in popularity in Australia, with Facebook one of the main platforms being used to provide anti-science material to skeptical parents.
The government launched a crackdown earlier this month on parents who did not vaccinate their children. The new proposals called, "No Jab, No Pay" will see welfare stripped from families who don't vaccinate.