The French cosmetic giant contracted Schiffer to promote its L'Oreal Perfect Slim and Wrinkle De-Crease brands using advertising agency McCann-Erickson to produce stylish television adverts extolling products' virtues.
But the Advertising Standards Agency believes the claims made in the adverts went too far.
For the wrinkle cream advert L'Oreal five complaints were made by members of the public against claims made in the advert. After a panel from the agency considered the complaints, three were upheld.
The wrinkle cream ad maintained that 76 per cent of users had reported a visible reduction in expression lines over a three week period and that wrinkles could be reduced in the space of just one hour, a claim that was considered to be excessive because it could be understood to have a 'physiological action with a cumulative effect'.
The ad also looked into claims about the product's inlcusion of Boswelox to counteract micro contractions. After consulting its own experts in the field, the agency said that L'Oreal's specific reference to the product's effects on expression lines were unsubstantiated - a point that was emphasized by Schiffer pulling a variety of different faces in the ad.
Moving on to the anti-cellulite product, the agency upheld two complaints made against Perfect Slim - the first that the product had been judged to be the best of its kind in an independent study and the second that 71 per cent of women had said it had visibly reduced the appearance of cellulite.
In upholding the complaint about the product being the best in its kind, the agency said that the evidence L'Oreal had produced to substantiate this was 'below the standard that would be expected to back up claims relating to physiological action'.
The complaint about the study was upheld because an ASA expert had examined the results of the trial but had found no evidence to support the claims, as it had been open and used no control or blind testing. Further details also proved that half of the individuals taking part in the study had not registered the improvement claimed.
L'Oreal has said that while it disagrees with the ASA's findings, it will be complying with the upheld claims and amending the adverts accordingly. The new adverts are expected to be aired on television by the end of the month.
The company also pointed out that both of the ads had already been approved by the Broadcast Advertising Clearance Centre after it had fulfilled requirements to substantiate all the claims the ads made.
In a statement L'Oreal said that, "Both L'Oreal Paris Wrinkle De-Crease and Perfect Slim have been very popular with customers, demonstrated not just by their overall sales, but also the repeat purchases.
"In addition, research that was presented to the ASA shows a high rate of satisfaction for both products: 92 per cent for Wrinkle De-Crease and 84 per cent for Perfect Slim."
Despite the claims by L'Oreal, the action taken by the British authorities points to mounting pressure to substantiate claims for cosmetics products that are said to make physical improvements to the appearance.
With formulations for anti-ageing products becoming increasingly sophisticated the boundaries of product efficacy are being constantly stretched. However, when it come to promoting the products, the ASA's most recent action equally means that there will be no room for ambiguity when it comes to efficacy claims.