Note: This advice is given by the CAP Executive about non-broadcast advertising. It does not constitute legal advice. It does not bind CAP, CAP advisory panels or the Advertising Standards Authority.


“Leading” claims are likely to be interpreted to mean best-selling, unless the ad makes an alternative meaning clear. “Leading” claims are comparative claims, and as such must comply with the rules comparisons (3.33 – 3.40). See Comparisons: General.

Leading claims
Alternative meanings

Leading claims

The ASA ruled against an ad which stated “the leading home show brand in the UK”, because whilst the advertisers had evidence relating to the total number of people involved in the show, including staff and exhibitors, the ASA considered that the claim would be interpreted to mean this show had the highest attendance rate of consumers compared to competing events (Media 10 Ltd, 30 August 2017).

In 2012, the ASA upheld a complaint against a human resources company’s claim to be “the UK’s market leader” in outplacement, because the company was unable to provide any data relating to their competitors’ sales figures (Penna plc, February 2014). Similarly, the claim “UK's leading 100% renewable electricity supplier" was found to be misleading because the advertiser was unable to provide comparative evidence to demonstrate that it had more customers on its 100% renewable electricity tariff than other companies did on theirs (Good Energy Ltd, August 2013).

Marketers should take care to ensure the basis of their leading claim is clear (Indo European Foods Ltd, January 2014).

Alternative meanings

If an advertiser intends to use “leading” to mean something other than best-selling, the ad should make this explicitly clear and the advertisers should have evidence. In 2001, the ASA disagreed with an advertiser’s contention that their “leading” claim was based on superior editorial quality and news content (Financial Times Business, January 2002). Similarly, in 2012, the ASA upheld complaints about a claim that a model engineering show was “the leading show of its kind” because the advertiser had not provided any evidence relating to visitor numbers. Their argument that the claim had been based on the number, content and variety of exhibits was rejected (Meridienne Exhibitions Ltd, January 2012).

Marketers may sometimes intend a “leading” claim to mean “first to the market” or “innovative”. For the ASA to accept that interpretation of the claim, marketers would need to have made it clear that a best-selling statement was not intended. In 2011, the ASA disagreed with an advertiser’s contention that their claim to be the “leading manufacturer of clean burning wood stoves” could be substantiated on the basis that they had introduced innovative features and innovations to the market that had since become standard in the industry, because the meaning of the claim was ambiguous (Clearview Stoves Ltd, April 2011). Similarly, in 2014, the ASA held that, in the absence of a clear indication that the intended comparison was between the technology and degree of innovation involved in the advertiser’s product and those of its competitors, the claim “the leading manufacturer of downdraught filter bench technology” would be regarded as a claim that the advertiser had the greatest share of the market (Air Cleaning Systems Ltd, February 2014). However, in 2013, the ASA accepted that the claim “world-leading technology”, which appeared alongside the claim “innovative solutions”, was likely to be understood by consumers as referring to the inventive nature of the product, rather than as a comparative claim regarding the advertiser’s market share (Eco Solutions, October 2013).

CAP recommends that marketers exercise caution when using “leading” to denote anything other than “best-selling” and ensure that any other intended meaning is both clear and supportable.

Advertisers must also ensure the claim is verifiable.


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