The advert for L'Oréal's anti-wrinkle cream featuring a striking photograph of Oscar-winning actor Rachel Weisz appeared too good to be true. "Skin looks smoother, complexion looks more even," said the double-page magazine spread. "It's not a facelift, it's Revitalift."

The industry watchdog, the Advertising Standards Authority, has ruled that the print advert must not appear again in its current form.

Rachel Weisz Photograph: Luke MacGregor/Reuters

Acting on a complaint from Liberal Democrat MP Jo Swinson, the regulator said the image of Weisz's face had been altered in post-production and had "substantially changed her complexion to make it appear smoother and more even" and "misleadingly exaggerated the performance of the product". The advert for Revitalift Repair 10 featured a close-up, black and white photograph of Weisz.

Swinson, co-founder of the Campaign for Body Confidence, last year successfully complained to the ASA that L'Oréal magazine ads featuring Julia Roberts, for Lancôme foundation product Teint Miracle, and Christy Turlington, for Maybelline foundation The Eraser, had been digitally enhanced.

"The beauty and advertising industries need to stop ripping off consumers with dishonest images," she said. "There needs to be much more diversity in advertising – different skin colours, body shapes, sizes and ages. Studies show that people want to see more authenticity from brands. Images can be aspirational without being faked."

L'Oréal said every effort had been made to make the picture more flattering, using a lot of light, and pointed out that the ASA had previously ruled that cosmetics adverts could present their product in the best possible light.

The ASA, in its ruling published on Wednesday, acknowledged that the advertisers were keen to present their products in their most positive light using techniques such as post-production enhancement and included the re-touching of images.

It said such techniques were acceptable "so long as the resulting effect was not one which misleadingly exaggerated the effect that the product was capable of achieving".

"Although we considered that the image in the advert did not misrepresent the luminosity or wrinkling of Rachel Weisz's face, we considered that the image had been altered in a way that substantially changed her complexion to make it appear smoother and more even," the ASA ruled.

"We therefore concluded that the image in the ad misleadingly exaggerated the performance of the product in relation to the claims 'skin looks smoother' and 'complexion looks more even'."

A spokesman for L'Oréal said they were disappointed to learn that the ASA had opposed their advertisement for Revitalift Repair 10. He said:" We do not believe the ad exaggerates the effect that can be achieved using this product."

The ASA told l'Oréal to ensure it "did not use post-production techniques in a way that misrepresented what was achievable using the advertised product".

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