The Advertising Standards Authority (ASA) said an advert by the firm, which claimed its fruit juice contained more antioxidants than the "five-a-day" portion, was not truthful or substantiated.
The verdict will come as a blow to Innocent and could set a precedent for other companies looking to make claims about antioxidant ability of fruit.
It also adds the pressure on speeding up EU rules, which will require all health claims to meet a Commission-improved list.
Although no official wording or accepted health claims have been approved, it seems that advertising regulators are already tightening up on health claims in preparation, and food companies should think carefully before making a health claim.
This is the second time in a week a company has come under fire for making a statement about a products' health or nutritional benefit.
Last week the UK Tea Council was criticised for exaggerating the benefits of tea, and banned from making further claims about the drinks' antioxidant potential after running a series of adverts .
Today the ASA said it had a complaint about Innocent's claim as to whether the product had a detoxifying effect and whether it contained more antioxidants than five average portions of fruit and vegetables per day.
The advert, which ran in national newspapers, said: " When we were inventing our natural detox superfoods smoothie, we figured we should use super berries from super trees, not weird artificial boosters from strange laboratories.
So we blended acai with equally incredible pomegranates and blueberries to produce a recipe that contains even more antioxidants than the average five a day.
We think it's the world's superest smoothie recipe.
Hope you like it too ."
In response to the complaint Innocent said the fruit in its smoothie contained high levels of antioxidants which neutralised the free radicals that could damage the body's cells.
The firm said that soaking up free radicals in this way therefore detoxified the body of free radicals.
Innocent also added that its product had an oxygen radical absorption capacity (ORAC) value of 1640 umol per 250 ml serving and that research showed a diet with an average five portions of fruit and vegetables per day contained an ORAC value of between 1470 and 1870 micromoles.
The ASA upheld both complaints and said it did not think Innocent's evidence proved the product removed toxins from the body.
The watchdog said that accepted nutritional advice says smoothies and fruit juice could count towards only one of the recommended five portions of fruit and vegetables per day, no matter how much was consumed.
The regulator said: " Even if the method of antioxidant calculation and the comparisons between fruit and vegetables and Innocent's product could be considered valid, we nevertheless noted that the ORAC value of 1640 micromoles per 250ml serving of Innocent Superfoods Smoothie was not "even more" than the antioxidant quantity of five portions of fruit and vegetables per day according to the study Innocent cited, but midway between the range of values it showed, the average of which was 1670 micromoles.
"We did not consider the evidence Innocent provided proved their product provided more antioxidants than five portions of fruit and vegetables per day."
The ASA ordered Innocent to stop the claims and to make sure the company used suitable evidence in support of future statements.
Innocent said it had no plans to use the claim again.
Speaking after the ruling co-founder Richard Reed said : "At innocent we've always tried to be clear in our communication with consumers.
We have absolutely no intention of misleading people.
The ad the ASA are talking about ran in October and has been withdrawn.
We want everyone to eat more fruit and vegetable, whether it's an innocent smoothie or a carrot from the greengrocer ."
Under regulation (EC) No 1924/2006, which came into force in the UK from 1 July 2007, any food product claiming to have a health benefit must meet a list of European Commission-approved wording and be supported by scientific evidence.
Although the regulation came into force this month in the UK, the European Commission is not expected to agree a list of approved literature until the end of the year.
The scope of the changes will not just affect food packaging, but any content including websites associated with the food.