Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. Keeley Foster, the LFB’s Deputy Assistant Commissioner, added: “Many ads continue to rely on outdated clichés that project firefighting as a male only job.“The ban on gender stereotype ads will hopefully help change attitudes and in turn encourage more women to embark on a wonderful and fulfilling career in the fire service.” One of Girlguiding’s Brownie and Guides group leaders, named only as Abigail, believes it “could make a huge change to the future of girls and young women”.”I think one advert that comes to mind is an Aptamil advert where babies were drinking milk, they had the exact same formula, but the girls were shown growing up to be ballerinas whereas the boys were shown growing up to be mathematicians,” she said.”That was purely based on gender, and I think the whole idea of you can’t be what you can’t see comes into play here. “Yes it’s ok for girls to be a mum or a ballerina, but you can also be a scientist or an astronaut and if we’re never showing the fact that you can do that then I don’t think you see those paths as being for you.”The LFB said portrayals of firefighting in the media are “a key barrier for young girls and women thinking of it as an achievable profession”. Female scientists, astronauts and firefighters should appear more in adverts following a new ban on “harmful” gender stereotypes, campaigners say.A rule to prevent sexist portrayals of men and women was introduced by The Committees of Advertising Practice (CAP) on Friday.It says adverts must not contain “gender stereotypes which are likely to cause harm or serious or widespread offence”.The ban will cover depictions of men struggling to change nappies, women who are unable to park and girls being less academic than boys.If an advert is complained about under the new code, the use of “humour” or “banter” is unlikely to be considered a valid defence. Campaigners hope it will spell the end of marketing like an 2017 advert for Aptamil milk which showed baby girls growing up to be ballerinas and boys growing up to be engineers and mountain climbers. The ASA said ads can still show people in gender-stereotypical roles, such as a woman cleaning or a man doing DIY, if they do not suggest that the “roles or characteristics shown are always uniquely associated with one gender”.They added: “Ads should be sensitive to the emotional and physical well-being of vulnerable groups of people who may be under pressure to conform to particular gender stereotypes. “The use of humour or ‘banter’ is unlikely to mitigate against the types of harm or serious or widespread offence identified in relation to gender stereotypes.” “A ‘it’s a joke’ defence, probably won’t be enough to convince the ASA that there isn’t a problem under the new rule.” Complaints about that advertising were not upheld at the time because the Advertising Standards Authority (ASA), which follows the CAH code, did not have the power to act on the grounds of gender stereotypes.Girlguiding, a charity for young women and girls, and the London Fire Brigade (LFB) were among the groups who encouraged the rule change during the consultation process.