Two magazine ads for cosmetics giant L'Oreal -- one for the Lancome brand featuring Julia Roberts and the other using Christy Turlington for Maybelline -- have been banned by U.K. watchdog the Advertising Standards Authority.

In both cases, L'Oreal was unable to prove it had not "overly airbrushed" the images of Ms. Roberts and Ms. Turlington, and the two magazine ads were banned for being "misleading" as well as for "exaggeration." Both ads were created by Interpublic Group of Cos.' Gotham , based in New York.

An ad for Maybelline's the Eraser foundation featured an image of Ms. Turlington. Parts of her face had been covered by the foundation, while other areas were left uncovered to show the effects of the product. The copy included the words "For ultimate flawless-looking perfection … The Eraser covers, fills and smooths precisely."

L'Oreal admitted it had used postproduction techniques to improve the image, but pointed out that lines under the eye, crows' feet, expression lines on the cheek and lines and pores near the model's nose were all clearly visible. The ASA, however, ruled that L'Oreal had provided insufficient evidence about the digital retouching of the images and banned the ad with immediate effect.

The ad for Lancome's Teint Miracle foundation featured a picture of Ms. Roberts taken by a famous fashion photographer, Mario Testino. L'Oreal claimed the photographer had used flattering light to reduce the imperfections, but the ASA rejected that . In its ruling, the ASA said, "On the basis of the evidence we received we could not conclude that the ad image accurately illustrated what effect the product could achieve."

Member of Parliament Jo Swinson made the complaints that initiated both investigations. She has waged a long-running campaign against unrealistic images of women in advertising under the banner "Campaign for Body Confidence." Today she posted on her website: "This ban sends a powerful message to advertisers -- let's get back to reality."

In the blog, Ms. Swinson claimed, "Shockingly, even the ASA weren't contractually allowed to see the pre-production photo of Julia Roberts. It shows just how ridiculous things have become when there is such fear over an un-airbrushed photo … both Christy Turlington and Julia Roberts are naturally beautiful women who don't need retouching to look great."

In 2007, the ASA banned a L'Oreal mascara ad featuring Penelope Cruz that claimed to deliver "up to 60% longer lashes." Ms. Cruz turned out to be wearing false lashes.

Lancome and Maybelline, however, remain defiant. Both issued statements saying they were "disappointed" that the ASA adjudicated against them, and defended their ads, claiming that they do not exaggerate the effects that their products can achieve.