Outspoken columnist Katie Hopkins has leapt to the defence of a controversial advert asking people: "Are you beach body ready?" after tens of thousands of people signed a petition demanding its removal.
A change.org petition against the Protein World advert has now attracted more than 43,000 signatures, and the Advertising Standards Agency has launched an investigation after receiving a torrent of complaints.
Some protesters have even taken to vandalising the posters, which have popped up in London Underground stations.
But Katie Hopkins, who has voiced criticism against overweight people in the past, took to Twitter to vent her anger against "chubsters" for using feminism as "an excuse to be fat".
"Society has huge acceptance for being fat - but masses of abuse for being skinny," she added.
Protein World has already been rapped by the advertising watchdog this year for making claims about the diet pills it sells online, which are not recognised as legitimate health products by the EU.
The petition against the advert states:
Critics, using the hashtag #EveryBodysReady, accused the firm of "body shaming" and began posting images of defaced versions of the poster, which promotes the use of meal replacement milkshakes and supplements.
Some argued that this encourages women to starve themselves, while others protested the idea of female bodies being used as a "commodity".
But the company and its supporters have remained unapologetic, accusing those complaining of "fit shaming" and being "sympathisers for fatties".
Protein World boss, Arjun Seth, added that sales had tripled since the controversy began - and said he had awarded his PR team a bonus for their flippant replies on social media.