Almost half of "healthy" breakfast bars contain similar or higher amounts of sugar than a bowl of Coco Pops, new research has found.
The breakfast biscuits are advertised as "a great start to your day" and "energy for the whole morning" but can contain up to four teaspoons of sugar, according to the study.
The research, released by campaign group Action on Sugar, found 46% of breakfast biscuits contain the same or more sugar than a 30g bowl of the Kellogg's chocolate cereal.
The survey analysed 39 breakfast biscuits sold in a number of UK supermarkets, with all of them containing at least one teaspoon of sugar.
Those with the highest sugar content include Lidl's Sondey Envitas chocolate and hazelnut breakfast biscuits and Belvita's Breakfast Cocoa with Choc Chip.
The research claimed that not one of the surveyed products featured the green colour coding - meaning low - for its sugar content.
It also found that 82% of products surveyed contain more sugar per serving than a 30g bowl of Honey Monster Puffs cereal.
The study comes as the Government is being urged to include clearer guidance on product labelling as part of its childhood obesity strategy to be published this year.
Jennifer Rosborough, campaign manager at Action on Sugar, said: "It is important that breakfast substitutes offer the healthiest alternative, rather than a worse option. Sadly, we could not recommend any of the products we examined which are laden with excess sugar.
"While some sugar in breakfast biscuits is naturally occurring due to ingredients such as fruit, many contain sugar that has been added by the manufacturer. We now want the Government to tackle this issue head on by making sure all manufacturers use colour-coded nutrition labelling, encouraging reductions in sugar, fat and salt and ensuring manufacturers promote their products responsibly."