An advert for Costa Coffee has been banned for urging customers to buy a bacon roll rather than avocados.
The radio ad featured a voiceover which said there was "a great deal on ripen-at-home avocados" but they will only "be ready to eat for about 10 minutes, then they'll go off".
The advert told people to choose the "better deal" of a roll or egg muffin.
Two listeners complained that the ad, which aired in June, discouraged people from opting for fresh fruit.
The advertising watchdog agreed with the complaints and upheld them.
Costa said its ad played on the "frustration and unpredictability of the avocado".
The chain claimed it was not suggesting that listeners must choose between the two breakfast options, but that it was instead telling people about its promotional offer.
The organisation which clears ads for broadcast, Radiocentre, said consumers would see the ad as a "light-hearted remark" about the experience of buying non-ripe avocados.
But in its ruling, the Advertising Standards Authority said consumers would interpret the ad as a comparison between the experience of eating an avocado and a bacon roll or egg muffin.
"We considered that, although the ad was light-hearted, it nevertheless suggested avocados were a poor breakfast choice, and that a bacon roll or egg muffin would be a better alternative, and in doing so discouraged the selection of avocados," the ASA said.
All radio and television adverts must comply with the UK Code of Broadcast Advertising (BCAP) which states that comparisons between foods must not discourage fruit and vegetables.
The advert must not be broadcast again, and Costa has been told to make sure its future ads do not "condone or encourage poor nutritional habits".