A survey of children's food in the East Midlands revealed a quarter of products tested had misleading nutritional information on packaging.
Trading Standards officers found one packet of crisps contained 150% more sugar than stated.
The survey focused on products aimed at children, often with cartoon characters on the labels.
Of the 200 tested, 53 samples were unsatisfactory. The main problem was inaccurate nutritional information.
Some had much more sugar or salt than was listed on the packaging.
Undeclared or illegal additives were also found in some samples.
The survey, which was one of the largest ever in the East Midlands, was conducted by the Trading Standards service.
They are now considering what further action can be taken.