The Advertising Standards Authority (ASA) has confirmed it has launched a formal investigation into the controversial Protein World advertising campaign, which has sparked an internet frenzy and a planned protest in Hyde Park tomorrow (2 May).

The advert posters, which picture a bikini-wearing model next to the slogan “Are you beach body ready?” have been branded “sexist” and “offensive”. More than 67,000 people had signed a petition at change.org by lunchtime on Friday calling for the posters to be banned.

The adverts were taken down by Transport for London (TFL) this week, having come to the end of their three-week contract period. A spokesperson said that the campaign did not contravene TFL’s advertising standards.

Meanwhile, the ASA confirmed the advert will not be allowed to appear again in its current form, because of concerns regarding the weight loss claims that are made.

The ASA said: "We've met with Protein World to discuss its "Are you beach body ready?" ad campaign.

"It's coming down in the next three days and, due to our concerns about a range of health and weight loss claims made in the ad, it can't appear again in its current form.

"Although the ad won't appear in the meantime, we've launched an investigation to establish if it breaks harm and offence rules or is socially irresponsible.

"We will now carefully and objectively explore the complaints that have prompted concerns around body confidence and promptly publish our findings."

The backlash against the advertising campaign for Protein World weight-loss products – which critics say promotes negative body issues – has continued to grow this week, with a mass demonstration planned for Hyde Park this weekend. Activists are planning a ‘Taking back the beach’ demonstration in Speaker’s Corner this Saturday, urging people of all sizes to attend in swimwear or whatever feels comfortable.

Throughout the furore, Protein World has maintained a robust defence of its campaign in numerous media appearances.

Protein World chief executive Arjun Seth told Channel 4 News that the ads were "aspirational" and said people critical of the campaign are "extremist, they shout a lot, these people are irrational and extremist, vandalising adverts."

The company claims that the controversy has been great for business and that it has helped attract more than 20,000 new followers to its Twitter account.

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