This Protein World ad was widely criticized for "sexism" last summer. Protein World The UK's advertising watchdog is launching a formal investigation into "gender stereotyping" in advertising.

The Advertising Standards Authority's (ASA) is calling for members of the public and organizations to submit evidence, according to a press release posted by ASA on Thursday.

This will form part of the ASA's research into the "objectification and sexualisation of women in ads."

Evidence could lead to a "change in regulation."

“We’re serious about making sure we’re alive to changing attitudes and behaviours," Guy Parker, chief executive of the ASA said. "That’s why we’ve already been taking action to ban ads that we believe reinforce gender stereotypes and are likely to cause serious and widespread offence, or harm."

The research comes as a result of "increasing political and public debate on equality issues," according to the press release.

Last summer the ASA received nearly 400 complaints about an ad by Protein World which featured a picture of a slim model next to the text "Are you beach body ready?"

More than 70,000 people signed an online petition calling for the ad to be removed from billboards. Critics claimed it was "sexist" and "fat-shaming."

The ASA banned the ad, but not because of sexism. Instead it was removed because of the health and weight loss claims made by the campaign.

The advertising watchdog said it would be "open-minded" about the prevalence and impact of gender stereotyping in advertising during its research.

Evidence can be sent to the ASA by email at: gender@asa.org.uk.