The model who emerged as a driving force in protecting young women in the industry from pressure to become dangerously thin has welcomed a move by one of the world’s most influential photo agencies to ban doctored stock images.

The move by Getty Images – whose photographs are widely used by media outlets around the world – takes effect today, just as a new French law comes in requiring that images that have been Photoshopped to change the size of a model be clearly labelled.

Getty’s new policy relates to freelance photographers who provide stock photography for a range of uses. The company already prohibits manipulation of images for news and events. On paid commercial assignments undertaken by Getty, retouching will continue to take place at a clients’ request.

Rosalie Nelson, who successfully petitioned for MPs to debate her cause after speaking out about being told to lose weight and get “down to the bone” – said Getty’s ban was a “great step”.

She told the Observer: “In most publications and advertisements, the models’ bodies have been distorted to make them appear healthier or a ‘more desirable shape’ – which can often mean a very thin model has had his or her body Photoshopped to look larger than it actually is. These same models are often asked to lose excessive amounts of weight and to diet obsessively.”

She also said she was heartened by changes evident at last month’s London fashion week but warned there were still problems with the way models look: “Although there were still a lot of thin and possibly underweight models, there was a lot more diversity throughout the shows. I’m optimistic that the whole industry will be more focused on health and body positivity in the next decade, rather than going for the ‘heroin chic’ look.”

The new French law comes days after Getty, the largest provider of stock photos in the world, emailed contributors requesting “that you do not submit to us any creative content depicting models whose body shapes have been retouched to make them look thinner or larger.”

Facebook Twitter Pinterest Rosalie Nelson Photograph: Ken McKay/ITV/Rex/Shutterstock

Rebecca Swift, director of creative planning at Getty, said that the company had already been moving in the direction of a ban but that the French law had been a catalyst. She told the Observer: “I have seen various trends come and go in terms of airbrushing and retouching but we are now very much in a period of authenticity where we are being ask to create more authentic content.

“We have about one million searches a day on our website so we have a very good sense of what the world is looking at. Over the last two years, and more markedly over the past year, we have seen a major increase in words like ‘real life’, ‘unstilted photography’ and ‘authenticity’ – especially around women.”

Campaigners want Britain to follow suit. Liam Preston, head of the YMCA’s body image campaign, Be Real, said: “I would love what the French have done to be introduced here because, if companies know this stipulation is there, they will be less likely to alter images.”

He said progress was being made in the UK, particularly in the wake of parliamentary inquiries into body image, but the issue did not appear to be a priority for the current government.

An all-party parliamentary group on body image has been discussing a possible new inquiry focusing on young people and the influence of social media, advertising and other sources. Others who have taken a stand on the issue are less convinced about the usefulness of government intervention.

Jo Swinson, the Lib Dem MP and former minister who has waged a long campaign against “overly perfected and unrealistic images” of women in advertising, said Getty’s policy was much more significant than the French law.

“I think it’s great that countries are looking to make this an issue but I think the practicalities of stating that an image has been retouched could apply to every single image if it is a blanket thing,” she told the Observer. “When you start to look at drafting a law, you find it doesn’t lend itself particularly well to legislation, partly because it’s very fast moving.”

Swinson emphasised the effect of campaigning and pressure for change on industries, citing her own complaints and others made more recently to the Advertising Standards Authority.

The ASA’s sister body, CAP – author of the UK Advertising Codes – is introducing new standards for advertisements that feature stereotypical gender roles or characteristics, following an ASA crackdown on “airbrushing”, which has seen the banning of beauty ads featuring stars such as Cara Delevingne, Natalie Portman and Julia Roberts.

So far this year, the ASA has received 150 complaints about 64 ads over their “depiction of weight”. In 2016, the authority received 301 complaints about 97 ads and 408 complaints about 75 ads the previous year

Caryn Franklin, the fashion commentator, activist and professor of diversity at Kingston University London, welcomed Getty’s new policy, but also warned that broader campaigns in the UK and elsewhere were as vital as ever. Franklin said she commended the actions of politicians such as Swinson, but emphasised the importance of grassroots change in the creative industries.

“It’s about alerting the next generation of creatives to the choices they might make around ethical presentations of women’s bodies and the impacts that can have,” she said. “That said, the more people in positions of power who express opinions on behalf of all our daughters the better.”