Last week Boots became the latest beauty advertiser to have product claims dismissed by the Advertising Standards Authority. The press ad, created by Mother, featured a slim woman casting a long shadow and ran with the lines "Super Slim No.7" and: "Anti-cellulite balm - a sleeker silhouette in 2 weeks."
Defending the ads, a spokesperson for Boots said: "No.7 Super Slim has shown itself in our testing to bring about visible results in 89 per cent of women tested. This is also backed by scientific evidence. The significantly increased market for these products in the past few years has shown customers are prepared to buy these products, and believe that they have benefits."
The ASA disagreed and ruled the ad was in breach of the rules on substantiation and truthfulness for health and beauty products. It ordered the retailer not to make future claims based solely on consumer perceptions.
The ASA's ruling follows a ban in August for McCann Erickson's ads for L'Oreal's Perfect Slim and Anti-Wrinkle De-Crease products, which starred the supermodel Claudia Schiffer.
The ASA found that there wasn't enough evidence to support either claim: Perfect Slim won't turn the average woman's thighs into those of Schiffer; nor will Wrinkle De-Crease cream work like Botox on worry lines.
Ads for cosmetics and shampoos from Chanel, Max Huber, Procter & Gamble and Dior have also been criticised by the ASA in the past.
With so many products on the shelves and so few bodies protecting the consumer's interests, it's reassuring to see the advertising watchdog occasionally stepping in. But, with an increasing number of bans, is the cosmetic industry suffering from a lack of credibility with consumers - a crisis caused by its own advertising?
Hamish Pringle, the director-general at the IPA, thinks not, arguing: "There is a perception that there are more complaints about cosmetic advertising.
In fact, the public is just hearing about them more." The logic behind the ASA's ruling, he says, is to increase the credibility of the cosmetics industry in the eyes of the consumer. "In general, the advertising industry is not frightened of complaints being upheld. It shows the system has some teeth and the consumer will know that you simply can't run ads that are illegal. It is only a good thing that there is a police dog out there that sometimes bites."
But as cosmetic ads increasingly focus on spurious scientific language and a dazzling array of clinical tests, does the watchdog need to tighten up the legislation surrounding cosmetics advertising?
The ASA thinks not: "There are firm guidelines as to what can and cannot be claimed in advertising, but there is always the devil in the detail, especially when modal verbs are used. Cosmetic companies aren't allowed to claim anything beyond a cosmetic effect. Claims made in advertising must be substantiated, and if they can't be, we will refer to a body of scientific and medical consultants," a spokesman says.
The sticking points seem to be not only the rigour of the scientific tests but also the question of what sample size the ASA accepts as credible.
Boots claimed that an independent study found 89 per cent of women who tested No.7 Super Slim said that they had seen positive results. Similarly, L'Oreal claimed that 76 per cent of women had "visibly reduced expression lines" after using Anti-Wrinkle De-Crease, and that 71 per cent of women found that Perfect Slim "visibly reduced the appearance of cellulite".
Neither company can confirm the sample size of its research panel. If these figures are to serve as the foundation for a major, science-based advertising campaign, the ASA feels it needs to be a realistic number.
Yet, if there is a decline in confidence, it's not translating into a decline in sales. UK women still spend an estimated £6 billion a year on beauty products. L'Oreal posted a £2.1 billion profit for 2004, a rise of 16.3 per cent.
Luke White, the co-founder of My Agency and a former creative director of McCann Erickson, where he oversaw work on L'Oreal (among other accounts), explains: "What woman wouldn't want to be as desired as the stars featured in the L'Oreal ads? It seems to me to be a triumph of hope over experience to believe that any cosmetics will turn the average woman into a supermodel, yet women want to believe that by applying some miracle cream they will somehow become younger or slimmer."
And even when the headlines trumpet "beauty products aren't doing what the ads say they are", women just don't want to hear it.
Annabel Jones, the beauty director at Eve magazine, says: "While it's worth remembering that a cellulite cream isn't going to turn you into Elle MacPherson, it's evident from television shows such as 10 Years Younger and reader response on women's magazines what a dramatic effect beauty products and treatments have on a woman's confidence.
"Far from losing its credibility, in recent years the beauty industry has embraced a more holistic, inside-out approach. Beauty is no longer about vanity, but about feeling good about yourself."
Marketing and science have got together and produced a hybrid form of sales experiment that has made its mark on advertising culture. The trouble is, women treat the claims made by cosmetics ads in the same way they treat horoscopes: they may well be nonsense, but sometimes it's just nice to believe in something.