The ASA is investigating Costa following a complaint from rival coffee chain Starbucks. Costa initially featured the line in a poster campaign it ran in March, stating it had based the figure on a survey of regular coffee shop customers.
The Costa ads also ran the line: "Sorry Starbucks – the people have voted". The ads were created by Karmarama.
However the small print stated the claim only compares a Costa cappuccino with those served in Caffe Nero and Starbucks. The latter has complained that the seven out of 10 claim is misleading because cappuccinos only reflect a small proportion of products sold in a coffee store.
The ASA confirmed it is investigating the campaign and has passed on part of the complaint, over Costa's use of the line in radio sponsorship, to Ofcom, which the regulator upheld. Additionally the radio ads did not contain the small print used on the print ads.
A story in The Times about the complaint states the ASA as recommending Costa is censured even though they disclosed the nature of the research in the ads. The ASA refused to comment on the claim and said the final adjudication would not be known for a number of weeks.
Last month Costa, which has 974 stores in the UK, reported like-for-like sales of 2.5% in the six months ending 27 August 2009.