A woman in a bikini! Ooh, quick cover her up!

Not very Facebook is it? How about a 'plus-size' woman in a bikini?

The social network has been forced to apologise for twice banning a picture of model Tess Holliday, which it claimed showed "undesirable body parts."

Ironically the snap, which shows a smiling Holliday posing in a black and white two-piece, was being used to promote body positivity.

Australian feminist group Cherchez la Femme had tried to pay to boost their presence on Facebook, but their ad for an upcoming conference, “Feminism and Fat” was rejected for “violating” Facebook's ad guidelines.

The group appealed the decision, only to be told Holliday's bikini shot “doesn't comply” with the company's “Health and Fitness Policy.”

“Ads may not depict a state of health or body weight as being perfect or extremely undesirable,” Facebook wrote. “Ads like these are not allowed since they make viewers feel bad about themselves. Instead, we recommend using an image of a relevant activity, such as running or riding a bike.”

“We’re raging pretty hard over here,” the group's organisers wrote in response to the ban. “Both because Facebook seemingly has no idea that plus sized, self describing fat women can feel great about themselves, and also because we haven’t been able to boost the original damn post.”

The picture and message that Holliday, 30, posted to her 1.2 million Instagram followers is a pretty spot-on lesson for Facebook's powers-that-be:

“Just because we’re plus size, doesn’t mean we have to prove that we’re healthy, just as someone who is smaller than us or average size doesn’t have to prove they are healthy,” she writes. “We should be able to exist in our bodies. I am technically healthy but my body is no more valid than someone’s who isn’t.”

Cherchez urged its supporters to spread the word about Facebook's justification for the ban - and saw its ad reinstated yesterday.

The social network, which has previously come under fire for removing pictures of women's nipples and breastfeeding, also apologised to the group.

“Our team processes millions of advertising images each week, and in some instances we incorrectly prohibit ads,” Facebook says in a statement. “This image does not violate our ad policies. We apologise for the error and have let the advertiser know we are approving their ad.”

Some more pictures of Holliday modelling her size 26 body for nobody's approval:

Want more? Holliday tells stylist.co.uk the stories behind her tattoos

Main image: Cherchez La Femme