Unilever has landed in hot water for claiming the majority of expert chefs prefer its Knorr brand to that of arch rival Bisto.

The company launched an ad campaign on the back of independent research based on the verdict of more than 60 chefs. However, the ASA this week ruled the ads, which had the strapline "unbeatable taste vs Bisto" were misleading.

It found that the claim was not actually substantiated by the research, and that most chefs had shown a preference for another product, the name of which is being kept under wraps.

The ASA was asked to ­investigate the ad by Bisto manufacturer Premier Foods, which claimed Unilever's ads "could not be substantiated".

Unilever said it had gone to "great lengths to ensure advertising was not ­misleading".