It asked consumers to tweet pictures of confusing or unrepresentative food labels under the hashtag #etiquetastrampa ('LabelTrap') as part of the ‘Do we know what we’re eating?’ campaign.
The OCU said it would then contact the company on behalf of the consumer and ask for the label to be changed.
Since the campaign began four days ago 500 tweets have been posted, reaching over one million Twitter users.
The aim of the campaign was to encourage companies to comply with the Food Information for Consumers Regulation (FIR) which came into force in December last year.
The website said in Spanish: “Through this campaign the OCU intends for the spirit of the regulations on labeling…to be respected.
“The OCU simply demands that consumers really know what they are buying: That the name of the food is clearly visible and does not have purely advertising goals."
Half of complaints concern food labels
It said that half of the food complaints it received still related to labels.
Common problems included companies failing to specify the percentage content of ingredients such as fruit or olive oil, or products which contained very little of a key ingredient but whose name suggested otherwise.
“Too often these claims are made simply to boost your purchase,” said the site.
One of the official campaign posters showed a picture of Knorr Lobster soup accompanied by the caption:
"This Gourmet Moments cream of lobster contains only 0.5% concentrated lobster, equivalent to 1.2 g in each packet. Would it not be more honest to call it shellfish soup, as it contains 5% shrimp?"
Some examples that consumers have posted on Twitter include a product called ‘Unsalted sunflower seeds’ which contained two ingredients - sunflower seeds and salt. Another was a jar of deer paté which contained nearly 80% pork.
Confusing for companies too?
But some companies have complained that understanding the new regulation has been an obstacle to implementation, despite the Food Drink Federation issuing special guidelines to help ensure compliance.
The checklist explained regulation on allergens, font size, nutrition information, vegetable oils and origin labelling.
More than a quarter (27%) of businesses surveyed in January by law firm Roythornes admitted they were unprepared for the regulations when the first phase was implemented last December.
But Peter Bennett of Roythornes said that it was still to soon for regulation enforcers to take serious action against examples of non-compliance and that companies were likely to be issued with an improvement notice.
“That said, non-compliance with an improvement notice is an offence in itself and food businesses will quickly find themselves in hot water should they not act quickly to implement necessary changes,” he told our sister publication Foodmanufacture.